Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 1.45 kb DNA sequence encoding the rat alpha 6 GABAA receptor subunit (nucleotides 33-1483) was cloned from a Sprague-Dawley rat brain cDNA library by PCR amplification. Dideoxy sequencing of two individual clones revealed that the nucleotide sequence differed at only one basepair (T480-->G) from that published previously. This difference altered the deduced amino acid sequence, producing a conservative amino acid substitution (His121-->Gln). A Gln residue is present at the same location in the bovine alpha 6 subunit. Restriction endonuclease analysis of the total PCR product demonstrated that this variant of the rat alpha 6 subunit was the only allele found in this particular rat brain library, the original allele was not present. These results were further verified by RNAse protection assays performed with RNA isolated from individual rat cerebella. alpha 6, beta 1, and gamma 2S subunits were transiently expressed in L929 cells for electrophysiological analysis. Whole-cell recordings obtained from the cells demonstrated that GABAA receptor channels with the expected GABA and benzodiazepine pharmacology were produced. Excised outside out single channel recordings from the same cells revealed that GABA elicited brief duration openings to a 33 pS main conductance level and to at least one smaller (approximately 21 pS) subconductance level. Thus this allelic variant of rat alpha 6 subunit could assemble with other subunits to form a functional GABAA receptor channel with similar properties to the original allelic form.
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PMID:Molecular and electrophysiological characterization of a allelic variant of the rat alpha 6 GABAA receptor subunit. 128 Dec 55

In this study, the endonuclease inhibitor aurintricarboxylic acid (ATA) was examined for its ability to attenuate both acute and delayed excitotoxicity mediated through NMDA and non-NMDA glutamate receptors. Ex vivo embryonic chick retina, a model system frequently used for studies of excitotoxicity, was exposed to either 100 microM NMDA or kainate (KA) +/- various concentrations of ATA for 60 min, then allowed to recover for 24 h. Lactate dehydrogenase release into the medium and histology were assessed as measures of delayed toxicity. ATA attenuated lactate dehydrogenase release due to NMDA or KA in a dose-dependent manner. Histology revealed that ATA decreased the number of pyknotic profiles in response to either glutamate agonist. The mechanism of ATA protection was addressed. ATA was found to block NMDA- but not KA-mediated 22Na+ influx and cyclic GMP formation. In membrane binding studies, ATA was relatively selective for displacement at the NMDA receptor. The IC50 values for displacement of [3H]CGS 19755, alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), or [3H]KA were 29.9 +/- 1.3, 313 +/- 46, and > 1,000 microM +/- SEM, respectively. ATA also fully attenuated NMDA-induced and partially attenuated KA-induced acute excitotoxicity as monitored histologically by tissue swelling and by the increase in GABA in the medium. Temporal studies of ATA efficacy indicated that ATA needed to be present during NMDA exposure to afford protection but, versus KA, was equally effective if administered immediately after KA exposure. Questions regarding the cellular penetration of ATA were raised because incubation with 100 microM ATA for 60 min had no effect on lactate formation or [3H]leucine incorporation into trichloroacetic acid-precipitable material, even though, in cell-free systems, ATA is a potent inhibitor of phosphofructokinase activity and protein synthesis. These studies demonstrate that ATA can protect against excitotoxicity mediated through NMDA or non-NMDA glutamate receptors. The mechanism of protection versus NMDA is through interruption of NMDA receptor interactions. ATA has no direct effect at the KA receptor; thus, its mechanism of protection versus KA is distinct from that versus NMDA and is, at present, unknown.
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PMID:Excitotoxicity at both NMDA and non-NMDA glutamate receptors is antagonized by aurintricarboxylic acid: evidence for differing mechanisms of action. 789 Nov 4

The effect of the endonuclease inhibitor aurintricarboxylic acid (ATA) versus NMDA-mediated delayed cell death was examined in an ex vivo chick retinal preparation. Transient exposure to 100 microM NMDA for 60 min followed by a 24-h recovery period resulted in a sevenfold increase in lactate dehydrogenase (LDH) release into the medium. ATA at 100 microM significantly reduced NMDA-mediated LDH release by 60%. In clarifying the mechanism of protection versus NMDA, ATA was found to inhibit several acute NMDA-mediated effects: ATA attenuated NMDA-mediated GABA release in a dose-dependent manner (IC50 = 29.5 microM), prevented NMDA-stimulated cyclic GMP formation, and blocked NMDA-mediated 22Na+ influx. These acute inhibitory effects of ATA were overcome by increasing the NMDA concentration, which suggested a competitive interaction between NMDA and ATA. In a binding assay using membranes prepared from adult rat forebrain, ATA displaced the competitive NMDA receptor ligand [3H]CGS 19755 with an IC50 of 26.9 microM. Maximal displacement was 88% with 100 microM ATA. These studies demonstrate that ATA protected neurons from NMDA-mediated cell death upstream of endonuclease inhibition, i.e., by antagonizing NMDA receptor activity in a manner consistent with competitive antagonism.
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PMID:Aurintricarboxylic acid prevents NMDA-mediated excitotoxicity: evidence for its action as an NMDA receptor antagonist. 839 May 67