Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Excitatory amino acid (EAA) receptor (EAAR) proteins purified from Xenopus central nervous system using a domoate affinity column and then separated into fractions using sucrose density gradient centrifugation were reconstituted, first into liposomes and then into planar lipid bilayers, using pipette-dipping and black lipid membrane techniques. Although the protein was eluted from the column with either alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) or kainate and could not be eluted with N-methyl-D-aspartate (NMDA), channel openings were obtained after exposure of the bilayers to kainate, AMPA, or NMDA (usually only in the presence of glycine). In bilayers exhibiting a single open channel conductance level this was approximately 6 pS with AMPA, approximately 9 pS with kainate, and approximately 50 pS with NMDA. However, with a few batches of protein unitary channel openings of up to 400 pS were observed, suggesting that reconstituted EAAR may sometimes form functional aggregates. The protein eluted from the domoate column was divided into two fractions on a sucrose density gradient. After reconstitution, one fraction responded to all three EAAs, whereas the other responded only to the non-NMDA receptor agonists. An explanation for these results is that some of the EAAR eluted from the column contain NMDA receptor subunits in addition to non-NMDA receptor subunits.
Mol Pharmacol 1993 Jul
PMID:Reconstitution of glutamate receptor proteins purified from Xenopus central nervous system into artificial bilayers. 768 68

N-methyl-D-aspartate (NMDA) receptor antagonists show therapeutic potential as neuroprotectants, analgesics, and anticonvulsants. In this context, we used electrical recording techniques to study the in vitro pharmacology of two novel quinoxalinediones, i.e., ACEA-1021 and ACEA-1031 (5-nitro-6,7- dichloro- and 5-nitro-6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione, respectively). Assays with NMDA receptors expressed by rat brain poly(A)+ RNA in Xenopus oocytes and with NMDA receptors in cultured rat cortical neurons indicated that ACEA-1021 and ACEA-1031 are potent competitive antagonists at NMDA receptor glycine sites. Apparent dissociation constants (Kb values) for ACEA-1021 and ACEA-1031 ranged between 6 and 8 nM for oocyte assays and between 5 and 7 nM for neuronal assays. Cloned NMDA receptors expressed in oocytes showed up to 50-fold variation in sensitivity, depending upon subunit composition. For example, using fixed agonist concentrations (10 microM glycine and 100 microM glutamate) IC50 values for ACEA-1021 with four binary combinations were as follows: NMDA receptor (NR)1A/2A, 29 nM; NR1A/2B, 300 nM; NR1A/2C, 120 nM; NR1A/2D, 1500 nM. Measurement of EC50 for glycine and calculation of Kb for the inhibitors indicated that differences in IC50 values are due to subunit-dependent variations in glycine affinity (EC50 ranged between approximately 0.1 and 1 microM) combined with variations in affinity of the antagonists themselves (Kb of approximately 2-13 nM). In addition to the strong antagonism of NMDA receptors, ACEA-1021 and ACEA-1031 were also moderately potent competitive inhibitors of non-NMDA receptors activated either by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid or by kainate. Antagonist affinities were similar whether measured with receptors expressed by rat brain poly(A)+ RNA in oocytes (Kb of 1-2 microM) or with cultured neurons (Kb of 1.5-3.3 microM). Our results suggest that the in vivo neuro-protective actions of ACEA-1021 and ACEA-1031 are predominantly due to inhibition at NMDA receptor glycine sites, although additional inhibition at non-NMDA receptors may play an ancillary role.
Mol Pharmacol 1995 Mar
PMID:In vitro pharmacology of ACEA-1021 and ACEA-1031: systemically active quinoxalinediones with high affinity and selectivity for N-methyl-D-aspartate receptor glycine sites. 770 Feb 54

Statin is a 57-kDa protein exclusively expressed in nuclei of nonproliferating mammalian cells. Recent studies have suggested that statin may play a role in the maintenance of growth arrest. Several lines of evidence also support the notion that a variety of genes and gene products are modulated during cell proliferation and cell death. The present study examined the possibility that statin expression could be modulated during neuronal injury using N-methyl-Daspartate (NMDA)-induced toxicity to rat embryonic hippocampal cultures as a model. Immunocytochemical studies using a monoclonal antibody to statin revealed a prominent nuclear localization of statin in cultured hippocampal cells. Western blot analysis showed that this antibody recognizes a 57-kDa protein band, indicative of the presence of statin in this preparation. Brief exposure of hippocampal neurons to NMDA (500 microM) produced severe neuronal degeneration over the subsequent hours. NMDA-treated neurons markedly overexpressed statin. Both NMDA-induced neuronal toxicity and statin overexpression were prevented by the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohept-5,10-imine hydrogen maleate (MK-801). Interestingly, time course studies indicate that the increased expression of statin observed following NMDA exposure clearly preceded the appearance of the first signs of neuronal death as determined by vital staining. In addition, exposure of hippocampal neurons to the Ca2+ ionophore, A23187, produced a marked increase in statin immunodetection, indicating that statin expression is likely regulated in a Ca(2+)-dependent manner. Thus, these results show that statin, which is expressed at low levels in embryonic rat cultured hippocampal neurons, is rapidly overexpressed following a toxic insult produced by the activation of the NMDA receptor. The observation that statin overexpression occurs prior to neuronal death raises the possibility that the up-regulation of statin could be used as an early index of neuronal injury.
Mol Cell Neurosci 1994 Dec
PMID:Statin, a marker of cell cycle arrest, is overexpressed during the early phase of delayed NMDA toxicity in hippocampal cell cultures. 770 26

Expression of c-fos mRNA after cortical injury was studied using the in situ hybridization technique. Strong signals for c-fos mRNA were observed immediately after cortical ablation in neurons throughout the cortex ipsilateral to the injury. However, this c-fos mRNA expression was transient and disappeared within 6 h after the injury. When basic fibroblast growth factor (bFGF; 1 micrograms) was applied to the site of ablation, c-fos mRNA signals were observed for a much longer period. Even 24 h after injury, diffuse expression of c-fos mRNA was detected throughout the cortex, being mainly confined to non-neuronal cells. Intraperitoneal injection of MK-801 (3 mg/kg), a non-competitive NMDA receptor antagonist, suppressed the expression of c-fos mRNA after cortical ablation. It suppressed both the immediate and late expression induced by cortical ablation and bFGF. The immediate expression of c-fos in neurons is likely to be due to spreading depression, while neuronal-glial interactions would be involved in the mechanism of late c-fos expression by non-neuronal cells. Our results suggest that induction of c-fos after cortical injury can be modulated by topically applied bFGF and that the N-methyl-D-aspartate (NMDA) receptor is involved in c-fos expression not only caused by injury itself but also induced by injury and bFGF. As the immediate early genes regulate secondary gene responses, the induction of c-fos may contribute to neuronal plasticity and bFGF may enhance its effect.
Brain Res Mol Brain Res 1995 Jan
PMID:Expression of c-fos mRNA after cortical ablation in rat brain is modulated by basic fibroblast growth factor (bFGF) and the NMDA receptor is involved in c-fos expression. 770 64

This study examines NMDAR1 receptor subunit mRNA expression and [125I]MK-801 binding in hypothalamic and limbic nuclei of intact, castrate and castrate-dihydrotestosterone propionate (DHTP)-treated male rats. In intact rats, the highest levels of NMDAR1 mRNA were observed in the supraoptic, suprachiasmatic, ventromedial and arcuate nuclei. Low levels of hybridization were observed in the bed nucleus of the stria terminalis, lateral preoptic area, lateral hypothalamic area and lateral septum. In castrated rats both NMDAR1 mRNA and [125I]MK-801 binding are significantly decreased in the lateral septum compared to castrate rats treated with DHTP, a non-aromatizable androgen. NMDAR1 mRNA was also significantly decreased in the supraoptic nucleus of castrate rats when compared to castrate rats treated with DHTP. These data suggest that androgens may modulate NMDA receptor function in some parts of the central nervous system.
Brain Res Mol Brain Res 1995 Jan
PMID:Distribution of NMDAR1 receptor subunit mRNA and [125I]MK-801 binding in the hypothalamus of intact, castrate and castrate-DHTP treated male rats. 770 78

Identification of the neurotransmitter receptor subtypes within the suprachiasmatic nuclei (SCN) will further understanding of the mechanism of the biological clock and may provide targets to manipulate circadian rhythms pharmacologically. We have focused on the ionotropic GABA and glutamate receptors because these appear to account for the majority of synaptic communication in the SCN. Of the 15 genes known to code for GABA receptor subunits in mammals we have examined the expression of 12 in the SCN, neglecting only the alpha 6, gamma 3, and rho 2 subunits. Among glutamate receptors, we have focused on the five known genes coding for the NMDA receptor subunits, and two subunits which help comprise the kainate-selective receptors. Expression was characterized by Northern analysis with RNA purified from a large number of mouse SCN and compared to expression in the remaining hypothalamus, cortex and cerebellum. This approach provided a uniform source of RNA to generate many replicate blots, each of which was probed repeatedly. The most abundant GABA receptor subunit mRNAs in the SCN were alpha 2, alpha 5, beta 1, beta 3, gamma 1 and gamma 2. The rho 1 (rho 1) subunit, which produces GABAC pharmacology, was expressed primarily in the retina in three different species and was not detectable in the mouse SCN despite a common embryological origin with the retina. For several GABA subunits we detected additional mRNA species not previously described. High expression of both genes coding for glutamic acid decarboxylase (GAD65 and GAD67) was also found in the SCN. Among the NMDA receptor subunits, NR1 was most highly expressed in the SCN followed in order of abundance by NR2B, NR2A, NR2C and NR2D. In addition, both GluR5 and GluR6 show clear expression in the SCN, with GluR5 being the most SCN specific. This approach provides a simple measure of receptor subtype expression, complements in situ hybridization studies, and may suggest novel isoforms of known subunits.
Brain Res Mol Brain Res 1995 Feb
PMID:GABAA, GABAC, and NMDA receptor subunit expression in the suprachiasmatic nucleus and other brain regions. 772 23

The functional effects of G protein-linked glutamate receptor activation have been studied in mouse mesencephalic neurons in vitro. We have been able to identify two receptor classes, one linked to phosphoinositide hydrolysis and another that inhibits adenylate cyclase. The agonist (1S,3R)-aminocyclopentane-1,3-dicarboxylate (ACPD) affected the two responses with similar potency (EC50 = 2 and 7 microM, respectively). In contrast, (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine selectively decreased adenylate cyclase activity (EC50 = 150 nM), without interfering with the phosphoinositide pathway. Activation of ion channel-linked glutamate receptors in mesencephalic neurons leads to cGMP formation. In this study, we demonstrate that cell pretreatment with ACPD or (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine prevented, in a dose-dependent fashion, N-methyl-D-aspartate (NMDA)-induced cGMP formation but not the kainate-stimulated response. The pharmacological profile suggests that receptors that are negatively coupled to adenylate cyclase are responsible for this effect. Coexposure of neurons to ACPD and Ba2+, a K+ channel blocker, counteracted the ACPD-induced blockade of NMDA receptors, suggesting that activation of K+ conductances could be involved in the post-transduction events triggered by metabotropic receptors in the mesencephalon. Neuronal treatment with NMDA for 10 min caused a reduction in mitochondrial activity. Direct inhibition of nitric oxide synthase with the inhibitor NG-nitro-L-arginine or removal of extracellular nitric oxide with reduced hemoglobin did not prevent this metabolic impairment, thus excluding a role for nitric oxide in this test for excitotoxicity. On the contrary, the mitochondrial function was maintained when neurons exposed to NMDA were preincubated with metabotropic receptor agonists. To summarize, our results suggest that metabotropic receptors that are negatively coupled to adenylate cyclase exert modulatory control specifically on NMDA receptor activity. This event could also contribute to the reduction of neurotoxic effects due to NMDA receptor hyperactivity.
Mol Pharmacol 1995 May
PMID:Metabotropic glutamate receptors negatively coupled to adenylate cyclase inhibit N-methyl-D-aspartate receptor activity and prevent neurotoxicity in mesencephalic neurons in vitro. 774 73

The effect of N-methyl-D-aspartate (NMDA) receptor blockade on the expression of preproenkephalin (PPE), preprotachykinin (PPT) and preprodynorphin (PPD) mRNAs in the caudate-putamen and nucleus accumbens was assessed with the non-competitive NMDA receptor antagonist MK-801. Administration of MK-801 once daily for 7 consecutive days increased the abundance of all three neuropeptide mRNAs in the caudate-putamen (CPU) and nucleus accumbens (NAc). (1) PPE mRNA abundance was increased in the anterior CPU (26%) as well as dorsal and ventral CPU (46% and 39%, respectively) but was unaffected in the NAc. (2) PPT mRNA was increased in the NAc (33%), anterior CPU (27%), dorsal CPU (43%) and ventral CPU (67%). In the ventral CPU, PPT mRNA abundance doubled when the dose of MK-801 increased two-fold (from 67% to 119% above control). (3) PPD mRNA was elevated in dorsal and ventral regions of the CPU (49% and 24%, respectively) and in anterior CPU (50%). In the NAc PPD mRNA was increased only at the higher dose (0.1 mg/kg) of MK-801. Cellular analysis of the distribution of grains per cell shows that increases are due to increased accumulation of mRNA by previously expressing cells of the CPU and NAc. These observations demonstrate that NMDA receptor activity plays a significant role in the regulation of neuropeptide expression in the caudate-putamen and accumbens of the rat brain.
Brain Res Mol Brain Res 1995 Mar
PMID:Elevation of striatal and accumbal preproenkephalin, preprotachykinin and preprodynorphin mRNA abundance subsequent to N-methyl-D-aspartate receptor blockade with MK-801. 776 91

Different NMDA receptor subunits have been recently cloned. The present paper describes the developmental profile of expression of the NR-1 subunit and three NR-2 subunits (A, B, C) in the rat central nervous system. A sensitive RNase protection assay was employed to determine simultaneously the mRNA levels of these receptor subunits. We found low levels of NR-1 mRNA (comprising all different splicing isoforms) in newborn rats with a progressive increase of its expression in the following 2-3 weeks. NR-2 subunits can be regarded as 'modulatory' since their expression can produce differences in the properties of NMDA receptors. More than one NR-2 subunits can be expressed in the same brain region. NR-2A and NR-2C are concomitantly expressed in the cerebellum and during development their mRNAs increase with a similar profile from low levels in P-8 rats to maximal expression in P-21 animals. NR-2A and NR-2B are concomitantly expressed in several brain regions with a different ontogenetic profile. In the hippocampus NR-2B mRNA increases rapidly during the first week of life as compared to the NR-2A subunits which at this time is expressed to low levels indicating that NR-2B will probably be dominant in determining the NMDA properties during the first period of life. Our data can provide a molecular correlate with properties of NMDA receptors such as voltage dependent Mg2+ block and deactivation kinetics which undergo significant changes during development and have been shown to depend upon the NR-2 subunit co-expressed with the common NR-1 subunit in various brain regions.
Brain Res Mol Brain Res 1994 Sep
PMID:Regulation of NMDA receptor subunit mRNA expression in the rat brain during postnatal development. 780 19

During lactation, there is an inhibition of cortical and hippocampal activation in response to N-methyl-D,L-aspartate (NMA), but not kainate, as assessed by induction of c-Fos expression. To study whether changes in NMDA receptor function may account for this inhibition, NMDA receptor subunit (NMDAR1) mRNA levels were measured by both Northern analysis and in situ hybridization. Analysis of NMDAR1 gene expression by Northern blot analysis did not reveal significant differences between cycling and lactating rats. Using in situ hybridization, NMDAR1 mRNA levels in several cortical and hippocampal areas appeared to be smaller in lactating rats, compared to cycling rats, although these differences reached significance only in the fronto-parietal cortex and piriform cortex. These subtle changes in NMDAR1 receptor subunit gene expression during lactation are not likely to account for the global lack of neuronal activation in response to NMA. However, it is possible that there may be changes in other NMDA receptor subunits that could account for the deficits in NMDA receptor activation. We also examined the activation state of afferent pathways in the brainstem that provide excitatory input to the cortex and hippocampus. During lactation, NMA induced c-Fos expression in similar areas of the brainstem as during the cycle, except in the locus coeruleus and dorsal raphe, where c-Fos expression was significantly less than that observed during the cycle. In contrast, no differences in the pattern of c-Fos expression in the brainstem in response to kainate were observed between cycling and lactating rats. The lack of NMA-induced activation of the locus coeruleus and dorsal raphe may contribute to the lack of cortical activation during lactation.
Brain Res Mol Brain Res 1994 Sep
PMID:Lactation-induced deficits in NMDA receptor-mediated cortical and hippocampal activation: changes in NMDA receptor gene expression and brainstem activation. 780 31


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