Activity-induced synaptic delivery of the GluN2A-containing NMDA receptor is dependent on endoplasmic reticulum chaperone Bip and involved in fear memory

The N-methyl-D-aspartate receptor (NMDAR) in adult forebrain is a heterotetramer mainly composed of two GluN1 subunits and two GluN2A and/or GluN2B subunits. The synaptic expression and relative numbers of GluN2A- and GluN2B-containing NMDARs play critical roles in controlling Ca²⁺-dependent signaling and synaptic plasticity. Previous studies have suggested that the synaptic trafficking of NMDAR subtypes is differentially regulated, but the precise molecular mechanism is not yet clear. In this study, we demonstrated that Bip, an endoplasmic reticulum (ER) chaperone, selectively interacted with GluN2A and mediated the neuronal activity-induced assembly and synaptic incorporation of the GluN2A-containing NMDAR from dendritic ER. Furthermore, the GluN2A-specific synaptic trafficking was effectively disrupted by peptides interrupting the interaction between Bip and GluN2A. Interestingly, fear conditioning in mice was disrupted by intraperitoneal injection of the interfering peptide before training. In summary, we have uncovered a novel mechanism for the activity-dependent supply of synaptic GluN2A-containing NMDARs, and demonstrated its relevance to memory formation.     

Involvement of the GluN2A and GluN2B Subunits in Synaptic and Extrasynaptic N-methyl-d-aspartate Receptor Function and Neuronal Excitotoxicity

GluN2A and GluN2B are the major subunits of functional NMDA receptors (NMDAR). Previous studies have suggested that GluN2A and GluN2B may differentially mediate NMDAR function at synaptic and extrasynaptic locations and play opposing roles in excitotoxicity, such as neurodegeneration triggered by ischemic stroke and brain injury. By using pharmacological and molecular approaches to suppress or enhance the function of GluN2A and GluN2B in cultured cortical neurons, we examined NMDAR-mediated, bidirectional regulation of prosurvival signaling (i.e. the cAMP response element-binding protein (CREB)-Bdnf cascade) and cell death. Inhibition of GluN2A or GluN2B attenuated the up-regulation of prosurvival signaling triggered by the activation of either synaptic or extrasynaptic NMDAR. Inhibition of GluN2A or GluN2B also attenuated the down-regulation of prosurvival signaling triggered by the coactivation of synaptic and extrasynaptic receptors. The effects of GluN2B on CREB-Bdnf signaling were larger than those of GluN2A. Consistently, compared with suppression of GluN2A, suppression of GluN2B resulted in more reduction of NMDA- and oxygen glucose deprivation-induced excitotoxicity as well as NMDAR-mediated elevation of intracellular calcium. Moreover, excitotoxicity and down-regulation of CREB were exaggerated in neurons overexpressing GluN2A or GluN2B. Together, we found that GluN2A and GluN2B are involved in the function of both synaptic and extrasynaptic NMDAR, demonstrating that they play similar rather than opposing roles in NMDAR-mediated bidirectional regulation of prosurvival signaling and neuronal death.     

In silico based unraveling of New Delhi metallo-β-lactamase (NDM-1) inhibitors from natural compounds: a molecular docking and molecular dynamics simulation study

Abstract

The development of pathogenic microbial resistance toward antibiotics has become a global clinical concern. New Delhi metallo-β-lactmase-1 (NDM-1) and its variants have recently drawn immense attention for its biological ability to catalyze the hydrolysis of almost all of β-lactam antibiotics including the Carbapenems which are generally considered as the last-resort antibiotics. Also, the horizontal gene transfer is expediting the rapid spread of NDM-1 in bacteria. In the wake of this serious antibiotic resistance problem it becomes imperative to find inhibitors which can render the present antibiotics functional and useful. In the present study, we have used Molecular docking and Molecular Dynamics (MD) simulation approach to find out suitable inhibitors against NDM-1 from an array of different natural compounds. We have screened unique natural compounds from ZINC database and also a set of standard antibiotics and inhibitors. Based upon the highest binding affinity demonstrated by docking with NDM-1, the best binding antibiotic Meropenem and the top five natural compounds, viz., Withaferin A, Beta-Sitosterol, Aristolochic acid, Diosgenin and Guggulsterone E were selected and subjected to MD simulations study. The docked NDM-1 complex with withaferin A, beta-sitosterol and diosgenin were found to be more stable as compared to the one with meropenem throughout the MD simulation process with the relative RMSD and RMSF in acceptable range. In conclusion, these compounds can be readily tested in vitro and in vivo to fully establish and confirm their inhibition potentiality and can also serve as lead molecules for the development of future functional inhibitors.

Communicated by Ramaswamy H. Sarma     

Exploration of interaction mechanism of tyrosol as a potent anti-inflammatory agent

Abstract

Drug discovery for a vigorous and feasible lead candidate is a challenging scientific mission as it requires expertise, experience, and huge investment. Natural products and their derivatives having structural diversity are renowned source of therapeutic agents since many years. Tyrosol (a natural phenylethanoid) has been extracted from olive oil, and its structure was confirmed by elemental analysis, FT-IR, FT-NMR, and single crystal X-ray crystallography. The conformational analysis for tyrosol geometry was performed by Gaussian 09 in terms of density functional theory. Validation of bond lengths and bond angles obtained experimentally as well as theoretically were performed with the help of curve fitting analysis, and values of correlation coefficient (R) obtained as 0.988 and 0.984, respectively. The charge transfer within the tyrosol molecule was confirmed by analysis of HOMO→LUMO molecular orbitals. In molecular docking with COX-2 (PDB ID: 5F1A), tyrosol was found to possess satisfactory binding affinity as compared to other NSAIDs (Aspirin, Ibuprofen, and Naproxen) and a COX-2 selective drug (Celecoxib). ADMET prediction, drug-likeness and bioactivity score altogether confirm the lead/drug like potential of tyrosol. Further investigation of simulation quality plot, RMSD and RMSF plots, ligands behavior plot as well as post simulation analysis manifest the consistency of 5F1A-tyrosol complex throughout the 20?ns molecular simulation process that signifies its compactness and stability within the receptor pocket. Abbreviations ADMET Absorption, Distribution, Metabolism, Excretion and Toxicity

Å Angstrom

COX-2 Cyclooxygenase-2

DFT Density Functional Theory

DMF Dimethylformamide

FMO Frontier Molecular Orbital

FT-IR Fourier-transform Infrared Spectroscopy

FT-NMR Nuclear Magnetic Resonance Spectroscopy

HOMO Highest Occupied Molecular Orbital

LUMO Lowest Unoccupied Molecular Orbital

MD Molecular Dynamics

NS Nanosecond

NSAIDs Non-steroidal anti-inflammatory drugs

OPE Osiris Property Explorer

RMSD Root-Mean-Square Deviation

RMSF Root Sean Square Fluctuation

Communicated by Ramaswamy H. Sarma     

Identification of novel natural inhibitors of Opisthorchis felineus cytochrome P450 using structure-based screening and molecular dynamic simulation

Opisthorchis felineus is the etiological agent of opisthorchiasis in humans. O. felineus cytochrome P450 (OfCYP450) is an important enzyme in the parasite xenobiotic metabolism. To identify the potential anti-opisthorchid compound, we conducted a structure-based virtual screening of natural compounds from the ZINC database (n = 1,65,869) against the OfCYP450. The ligands were screened against OfCYP450 in four sequential docking modes that resulted in 361 ligands having better docking score. These compounds were evaluated for Lipinski and ADMET prediction, and 10 compounds were found to fit well with re-docking studies. After refinement by docking and drug-likeness analyses, four potential inhibitors (ZINC2358298, ZINC8790946, ZINC70707116, and ZINC85878789) were identified. These ligands with reference compounds (itraconazole and fluconazole) were further subjected to molecular dynamics simulation (MDS) and binding energy analyses to compare the dynamic structure of protein after ligand binding and the stability of the OfCYP450 and bound complexes. The binding energy analyses were also calculated. The results suggested that the compounds had a negative binding energy with ?259.41, ?110.09, ?188.25, ?163.30, ?202.10, and ?158.79 kJ mol^?1 for itraconazole, fluconazole, and compounds with IDs ZINC2358298, ZINC8790946, ZINC70707116, and ZINC85878789, respectively. These lead compounds displayed significant pharmacological and structural properties to be drug candidates. On the basis of MDS results and binding energy analyses, we concluded that ZINC8790946, ZINC70707116, and ZINC85878789 have excellent potential to inhibit OfCYP450.     

In silico docking and molecular dynamics simulation of 3-dehydroquinate synthase (DHQS) from <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>

The shikimate pathway is as an attractive target because it is present in bacteria, algae, fungi, and plants but does not occur in mammals. In Mycobacterium tuberculosis (MTB), the shikimate pathway is integral to the biosynthesis of naphthoquinones, menaquinones, and mycobactin. In these study, novel inhibitors of 3-dehydroquinate synthase (DHQS), an enzyme that catalyzes the second step of the shikimate pathway in MTB, were determined. 12,165 compounds were selected from two public databases through virtual screening and molecular docking analysis using PyRx 8.0 and Autodock 4.2, respectively. A total of 18 compounds with the best binding energies (?13.23 to ?8.22 kcal/mol) were then selected and screened for absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis, and nine of those compounds were found to satisfy all of the ADME and toxicity criteria. Among those nine, the three compounds—ZINC633887?(binding energy =??10.29 kcal/mol), ZINC08983432?(?9.34 kcal/mol), and PubChem73393?(?8.61 kcal/mol)—with the best binding energies were further selected for molecular dynamics (MD) simulation analysis. The results of the 50-ns MD simulations showed that the two compounds ZINC633887 and PubChem73393 formed stable complexes with DHQS and that the structures of those two ligands remained largely unchanged at the ligand-binding site during the simulations. These two compounds identified through docking and MD simulation are potential candidates for the treatment of TB, and should undergo validation in vivo and in vitro.     

Casein kinase 2-mediated synaptic GluN2A up-regulation increases N-methyl-D-aspartate receptor activity and excitability of hypothalamic neurons in hypertension

Increased glutamatergic input, particularly N-methyl-D-aspartate receptor (NMDAR) activity, in the paraventricular nucleus (PVN) of the hypothalamus is closely associated with high sympathetic outflow in essential hypertension. The molecular mechanisms underlying augmented NMDAR activity in hypertension are unclear. GluN2 subunit composition at the synaptic site critically determines NMDAR functional properties. Here, we found that evoked NMDAR-excitatory postsynaptic currents (EPSCs) of retrogradely labeled spinally projecting PVN neurons displayed a larger amplitude and shorter decay time in spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rats. Blocking GluN2B caused a smaller decrease in NMDAR-EPSCs of PVN neurons in SHRs than in WKY rats. In contrast, GluN2A blockade resulted in a larger reduction in evoked NMDAR-EPSCs and puff NMDA-elicited currents of PVN neurons in SHRs than in WKY rats. Blocking presynaptic GluN2A, but not GluN2B, significantly reduced the frequency of miniature EPSCs and the firing activity of PVN neurons in SHRs. The mRNA and total protein levels of GluN2A and GluN2B in the PVN were greater in SHRs than in WKY rats. Furthermore, the GluN2B Ser(1480) phosphorylation level and the synaptosomal GluN2A protein level in the PVN were significantly higher in SHRs than in WKY rats. Inhibition of protein kinase CK2 normalized the GluN2B Ser(1480) phosphorylation level and the contribution of GluN2A to NMDAR-EPSCs and miniature EPSCs of PVN neurons in SHRs. Collectively, our findings suggest that CK2-mediated GluN2B phosphorylation contributes to increased synaptic GluN2A, which potentiates pre- and postsynaptic NMDAR activity and the excitability of PVN presympathetic neurons in hypertension.     

Ligand-based pharmacophore mapping and virtual screening for identification of potential discoidin domain receptor 1 inhibitors

Abbreviations ADME absorption, distribution, metabolism, and excretion

MMGB/SA molecular mechanics generalized born surface area

IFD induced fit docking

RTK receptor tyrosine kinase

NSCLC non-small-cell lung cancer

ATP adenosine triphosphate

OPLS optimized potential for liquid stimulation

RMSD root mean square deviation

HTVS high-throughput virtual screening

SP standard precision

XP extra precision

OPLS-AA optimized potential for liquid stimulation-all atom

MD molecular simulation

MME molecular mechanics energies

SGB surface generalized born

POPC membrane 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membrane

PDB Protein Data Bank

DDR1 discoidin domain receptor 1

DDR2 discoidin domain receptor 2

DDRs discoidin domain receptors

ECM extracellular matrix

TIP4P transferable intermolecular potential 4 point

NPT constant particle number, pressure and temperature

RMSF root mean square fluctuation

Communicated by Ramaswamy H. Sarma     

Structure-based screening and molecular dynamics simulations offer novel natural compounds as potential inhibitors of Mycobacterium tuberculosis isocitrate lyase

Mycobacterium tuberculosis is the etiological agent of tuberculosis in humans and is responsible for more than two million deaths annually. M. tuberculosis isocitrate lyase (MtbICL) catalyzes the first step in the glyoxylate cycle, plays a pivotal role in the persistence of M. tuberculosis, which acts as a potential target for an anti-tubercular drug. To identify the potential anti-tuberculosis compound, we conducted a structure-based virtual screening of natural compounds from the ZINC database (n = 1,67,748) against the MtbICL structure. The ligands were docked against MtbICL in three sequential docking modes that resulted in 340 ligands having better docking score. These compounds were evaluated for Lipinski and ADMET prediction, and 27 compounds were found to fit well with re-docking studies. After refinement by molecular docking and drug-likeness analyses, three potential inhibitors (ZINC1306071, ZINC2111081, and ZINC2134917) were identified. These three ligands and the reference compounds were further subjected to molecular dynamics simulation and binding energy analyses to compare the dynamic structure of protein after ligand binding and the stability of the MtbICL and bound complexes. The binding free energy analyses were calculated to validate and capture the intermolecular interactions. The results suggested that the three compounds had a negative binding energy with ?96.462, ?143.549, and ?122.526 kJ mol^?1 for compounds with IDs ZINC1306071, ZINC2111081, and ZINC2134917, respectively. These lead compounds displayed substantial pharmacological and structural properties to be drug candidates. We concluded that ZINC2111081 has a great potential to inhibit MtbICL and would add to the drug discovery process against tuberculosis.     

Surface dynamics of GluN2B‐NMDA receptors controls plasticity of maturing glutamate synapses

NMDA‐type glutamate receptors (NMDAR) are central actors in the plasticity of excitatory synapses. During adaptive processes, the number and composition of synaptic NMDAR can be rapidly modified, as in neonatal hippocampal synapses where a switch from predominant GluN2B‐ to GluN2A‐containing receptors is observed after the induction of long‐term potentiation (LTP). However, the cellular pathways by which surface NMDAR subtypes are dynamically regulated during activity‐dependent synaptic adaptations remain poorly understood. Using a combination of high‐resolution single nanoparticle imaging and electrophysiology, we show here that GluN2B‐NMDAR are dynamically redistributed away from glutamate synapses through increased lateral diffusion during LTP in immature neurons. Strikingly, preventing this activity‐dependent GluN2B‐NMDAR surface redistribution through cross‐linking, either with commercial or with autoimmune anti‐NMDA antibodies from patient with neuropsychiatric symptoms, affects the dynamics and spine accumulation of CaMKII and impairs LTP. Interestingly, the same impairments are observed when expressing a mutant of GluN2B‐NMDAR unable to bind CaMKII. We thus uncover a non‐canonical mechanism by which GluN2B‐NMDAR surface dynamics plays a critical role in the plasticity of maturing synapses through a direct interplay with CaMKII.     

A deficiency of the GluN2C subunit of the N-methyl-D-aspartate receptor is neuroprotective in a mouse model of ischemic stroke

The N-methyl-D-aspartate receptor (NMDAR) ion channel plays a pivotal role in the pathology of ischemic stroke. The functional receptor consists of two GluN1 subunits (a-h) and two GluN2 subunits (A/B/C/D), the expression of which are spatially and temporally regulated in pathological and physiological conditions. While the roles of the GluN2A and GluN2B subunit in ischemic stroke have been well developed, the role of the GluN2C subunit in ischemia is not well understood. Following middle carotid artery occlusion (MCAO), GluN2C^-/- male mice displayed similar volumes of infarct as wild-type (WT) mice. However, GluN2C^-/- mice showed decreased cerebral edema and an enhanced rate of neurological recovery compared to WT mice. The ischemic penumbra of GluN2C^-/- mice showed fewer cytoarchitectural deficits and decreased tauopathy relative to WT mice. These neuroprotective changes in GluN2C^-/- mice also corresponded with decreased expression of Fyn kinase and decreased phosphorylation of GluN2B subunit at Tyr1336. Lastly, a GluN2C deficiency modified the NMDAR/pro-survival signaling axis, as shown by increased levels of nuclear CREB(P-Ser133). Thus, the GluN2C subunit enhances ischemic stroke pathology by promoting neuronal dysfunction in the penumbra region.     

Phosphorylation of Tyrosine 1070 at the GluN2B Subunit Is Regulated by Synaptic Activity and Critical for Surface Expression of N-Methyl-d-aspartate (NMDA) Receptors

The number and subunit composition of synaptic N-methyl-d-aspartate receptors (NMDARs) play critical roles in synaptic plasticity, learning, and memory and are implicated in neurological disorders. Tyrosine phosphorylation provides a powerful means of regulating NMDAR function, but the underling mechanism remains elusive. In this study we identified a tyrosine site on the GluN2B subunit, Tyr-1070, which was phosphorylated by a proto-oncogene tyrosine-protein (Fyn) kinase and critical for the surface expression of GluN2B-containing NMDARs. The phosphorylation of GluN2B at Tyr-1070 was required for binding of Fyn kinase to GluN2B, which up-regulated the phosphorylation of GluN2B at Tyr-1472. Moreover, our results revealed that the phosphorylation change of GluN2B at Tyr-1070 accompanied the Tyr-1472 phosphorylation and Fyn associated with GluN2B in synaptic plasticity induced by both chemical and contextual fear learning. Taken together, our findings provide a new mechanism for regulating the surface expression of NMDARs with implications for synaptic plasticity.     

Identification of natural compounds as potent inhibitors of SARS-CoV-2 main protease using combined docking and molecular dynamics simulations

Coronavirus disease 2019 (COVID-19) has emerged from China and globally affected the entire population through the human-to-human transmission of a newly emerged virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The genome of SARS-CoV-2 encodes several proteins that are essential for multiplication and pathogenesis. The main protease (M^pro or 3CL^pro) of SARS-CoV-2 plays a central role in its pathogenesis and thus is considered as an attractive drug target for the drug design and development of small-molecule inhibitors. We have employed an extensive structure-based high-throughput virtual screening to discover potential natural compounds from the ZINC database which could inhibit the M^pro of SARS-CoV-2. Initially, the hits were selected on the basis of their physicochemical and drug-like properties. Subsequently, the PAINS filter, estimation of binding affinities using molecular docking, and interaction analyses were performed to find safe and potential inhibitors of SARS-CoV-2 M^pro. We have identified ZINC02123811 (1-(3-(2,5,9-trimethyl-7-oxo-3-phenyl-7H-furo[3,2-g]chromen-6-yl)propanoyl)piperidine-4-carboxamide), a natural compound bearing appreciable affinity, efficiency, and specificity towards the binding pocket of SARS-CoV-2 M^pro. The identified compound showed a set of drug-like properties and preferentially binds to the active site of SARS-CoV-2 M^pro. All-atom molecular dynamics (MD) simulations were performed to evaluate the conformational dynamics, stability and interaction mechanism of M^pro with ZINC02123811. MD simulation results indicated that M^pro with ZINC02123811 forms a stable complex throughout the trajectory of 100 ns. These findings suggest that ZINC02123811 may be further exploited as a promising scaffold for the development of potential inhibitors of SARS-CoV-2 M^pro to address COVID-19.     

In silico screening of anti-inflammatory compounds from Lichen by targeting cyclooxygenase-2

Abstract

Non-steroidal anti-inflammatory drugs (NSAID) targeting cyclooxygenase-2 are clinically effective. However, they lack anti-thrombotic activity resulting in incidences of adverse effects like myocardial infarction, gastrointestinal and abdominal discomfort which necessitate for discovering new drug candidates with improved therapeutic effects and tolerability. Various recent researches have suggested that many lichens offer a vast reservoir for anti-inflammatory drug candidates which are natural as well as safe for human consumption. Drug discovery is a very complex and time-consuming process; however, in silico techniques can make this process simple and economic. Hence to find out natural anti-inflammatory compounds, we have carried out the virtual screening of 412 lichen compounds by molecular docking with human Cox-2 enzyme and validated the docking score by X-Score followed by ADMET and Drug-likeness analysis. The resulting 6 top-scored compounds were subjected to Molecular dynamics simulation (MDS) to analyze the stability of docked protein-ligand complex, to assess the fluctuation and conformational changes during protein-ligand interaction. The values of RMSD, Rg, and interaction energy after 30?ns of MDS revealed the good stability of these Lichen compounds in the active site pocket of Cox-2 in compare to reference, JMS. Additionally, we have done the pharmacophore analysis which found many common pharmacophore features between Lichen compounds and well known anti-inflammatory compounds. Our result shows that these lichen compounds are potential anti-inflammatory candidates and could be further modified and evaluated to develop more effective anti-inflammatory drugs with fewer side effects for the treatment of inflammatory diseases.

Communicated by Ramaswamy H. Sarma     

Identification of potential leukocyte antigen-related protein (PTP-LAR) inhibitors through 3D QSAR pharmacophore-based virtual screening and molecular dynamics simulation

Abstract

Owing to its negative regulatory role in insulin signaling, protein tyrosine phosphatase of leukocyte antigen-related protein (PTP-LAR) was widely thought as a potential drug target for diabetes. Now, it was urgent to search for potential LAR inhibitors targeting diabetes. Initially, the pharmacophore models of LAR inhibitors were established with the application of the HypoGen module. The cost analysis, test set validation, as well as Fischer’s test was used to verify the efficiency of pharmacophore model. Then, the best pharmacophore model (Hypo-1-LAR) was applied for the virtual screening of the ZINC database. And 30 compounds met the Lipinski’s rule of five. Among them, 10 compounds with better binding affinity than the known LAR inhibitor (BDBM50296375) were discovered by docking studies. Finally, molecular dynamics simulations and post-analysis experiments (RMSD, RMSF, PCA, DCCM and RIN) were conducted to explore the effect of ligands (ZINC97018474 and Compound 1) on LAR and preliminary understand why ZINC97018474 had better inhibitory activity than Compound 1 (BDBM50296375).

Communicated by Ramaswamy H. Sarma     

Structure based docking and molecular dynamics studies: Peroxisome proliferator-activated receptors –α/γ dual agonists for treatment of metabolic disorders

Abstract

Diabetes is a foremost health problem globally susceptible to increased mortality and morbidity. The present therapies in the antidiabetic class have sound adverse effects and thus, emphasis on the further need to develop effective medication therapy. Peroxisome proliferator-activated receptor alpha-gamma dual approach represents an interesting target for developing novel anti-diabetic drug along with potential anti-hyperlipidimic activity. In the current study, the peroxisome proliferator-activated receptor alpha-gamma agonistic hits were screened by hierarchical virtual screening of drug like compounds followed by molecular dynamics simulation and knowledge-based structure-activity relation analysis. The key amino acid residues of binding pockets of both target proteins were acknowledged as essential and were found to be associated in the key interactions with the most potential dual hit. This dual targeted approach of structure based computational technique was undertaken to identify prevalent promising hits for both targets with binding energy and absorption distribution metabolism excretion prediction supported the analysis of their pharmacokinetic potential. In addition, stability analysis using molecular dynamics simulation of the target protein complexes was performed with the most promising dual targeted hit found in this study. Further, comparative analysis of binding site of both targets was done for the development of knowledge-based structure-activity relationship, which may useful for successful designing of dual agonistic candidates. Abbreviations ADME absorption distribution metabolism excretion

HTVS highthroughput virtual screening

MD molecular dynamics

MMGBSA molecular mechanics generalized bonn solvation accessible

PDB protein data bank

PPAR peroxisome proliferator-activated receptor

RMSD Root mean square deviation

RMSF Root mean square fluctuation

SAR structural activity relationship

SP simple precision

T2DM TypeII diabetes mellitus

XP Extra precision

Communicated by Ramaswamy H. Sarma     

The subtype of GluN2 C-terminal domain determines the response to excitotoxic insults

It is currently unclear whether the GluN2 subtype influences NMDA receptor (NMDAR) excitotoxicity. We report that the toxicity of NMDAR-mediated Ca(2+) influx is differentially controlled by the cytoplasmic C-terminal domains of GluN2B (CTD(2B)) and GluN2A (CTD(2A)). Studying the effects of acute expression of GluN2A/2B-based chimeric subunits with reciprocal exchanges of their CTDs revealed that CTD(2B) enhances NMDAR toxicity, compared to CTD(2A). Furthermore, the vulnerability of forebrain neurons in?vitro and in?vivo to NMDAR-dependent Ca(2+) influx is lowered by replacing the CTD of GluN2B with that of GluN2A by targeted exon exchange in a mouse knockin model. Mechanistically, CTD(2B) exhibits stronger physical/functional coupling to the PSD-95-nNOS pathway, which suppresses protective CREB activation. Dependence of NMDAR excitotoxicity on the GluN2 CTD subtype can be overcome by inducing high levels of NMDAR activity. Thus, the identity (2A versus 2B) of the GluN2 CTD controls the toxicity dose-response to episodes of NMDAR activity.