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)

Benzodiazepines have been shown to competitively inhibit morphine glucuronidation in rat and human hepatic microsomes. Flunitrazepam exerted a potent competitive inhibition of rat hepatic morphine UDP-glucuronosyltransferase (UDPGT) activity (Ki = 130 microM). It has no effect on the activity of p-nitrophenol, 17 beta-hydroxysteroid, 3 alpha-hydroxysteroid, or 4-hydroxybiphenyl UDPGTs. Because flunitrazepam is an effective photoaffinity label for benzodiazepine receptors, studied were performed in solubilized rat hepatic microsomes and with partially purified preparations of morphine UDPGT to determine the enhancement of flunitrazepam inhibition and binding to morphine UDPGT promoted by exposure to UV light. Under UV light, flunitrazepam inhibition was markedly enhanced. UV light exposure also led to a marked increase in binding of [3H]flunitrazepam to microsomal protein, which was protected substantially by preincubation with morphine. Testosterone, androsterone, and UDP-glucuronic acid did not protect against UV-enhanced flunitrazepam binding, and morphine did not reverse flunitrazepam binding once binding had occurred. As morphine UDPGT was purified, a good correlation was found between the increases in specific activity of morphine UDPGT and flunitrazepam binding to protein. Chromatofocusing chromatography showed that flunitrazepam bound only to fractions containing active morphine UDPGT, and no binding to 4-hydroxybiphenyl UDPGT was observed. Fluorography of a sodium dodecyl sulfate-polyacrylamide electrophoresis gel of solubilized hepatic microsomes that had been treated with [3H] flunitrazepam under UV light revealed a band with a monomeric molecular weight between 54,000 and 58,000. This monomeric molecular weight compares favorably with the reported monomeric molecular weight of homogeneous morphine UDPGT (56,000). These studies suggest that flunitrazepam binds rather selectively to the morphine binding site of morphine UDPGT and may prove to be a useful probe for this enzyme.
Mol Pharmacol 1990 Sep
PMID:Photoaffinity labeling of rat liver microsomal morphine UDP-glucuronosyltransferase by [3H]flunitrazepam. 211 76

Various alpha and beta 3 subunit-specific antibodies were used to characterize some of the heterogeneous ligand-binding properties of gamma-aminobutyric acidA receptors. Polyclonal antibodies that were raised against the cytoplasmic amino acid sequence (380-392) of the rat beta 3 subunit recognized a single polypeptide of molecular mass of 58 kDa in Western blots with Ro7-1986 affinity-purified GABAA receptors from the rat brain, and a doublet of molecular mass of 54 kDa and 56 kDa in receptors from the bovine cortex, hippocampus, and cerebellum. Deglycosylation of purified receptors from the bovine cortex with N-glycanase resulted in a single band immunostained at molecular mass of 52 kDa. These anti-beta 3 subunit antibodies immunoprecipitated approximately 50% of [3H]flunitrazepam binding sites from soluble extracts of bovine cortex, whereas beta cyto antibodies, which probably recognize all beta subunit isoforms, precipitated almost 100% of benzodiazepine binding sites. These results indicate heterogeneity of GABAA receptor subunit composition with respect to the nature of beta subunits. The GABA analogue 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), like GABA, shows heterogeneous binding affinities in brain homogenates. The higher affinity sites were previously suggested as corresponding to a 58-kDa polypeptide in rat that is photoaffinity-labeled with [3H]muscimol, a band that comigrates with the one stained by anti-beta 3 antibodies. However, THIP affinity was not significantly different between receptors containing beta 3 subunits and those lacking beta 3, as demonstrated by similar affinities in receptors that ere immunoprecipitated by anti-beta 3 antibodies and those that were not. Also, THIP displaced [3H]muscimol binding with similar multiple affinities across brain regions where different beta subunit variants are expressed with varying abundances. These observations suggest that the property of high affinity THIP binding cannot be explained solely by beta 3 subunits. The coupling efficiency between GABA and benzodiazepine binding sites appears to be determined by the nature of alpha subunits rather than of beta subunits. GABA enhanced [3H]flunitrazepam binding with different efficacies and potencies in receptors immunoprecipitated by anti-alpha 1, -alpha 2, and -alpha 3 subunit antibodies. In contrast, beta 3 subunit-enriched and disenriched receptors did not differ in this property. [3H]Flunitrazepam binding in GABAA receptors containing alpha 2 and alpha 3 subunits was enhanced to a significantly greater extent than were those with alpha 1. In addition, receptors containing alpha 1 and alpha 3 subunits had higher potencies of enhancement than did those with alpha 2 subunits.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1995 Oct
PMID:Pharmacological subtypes of the gamma-aminobutyric acidA receptors defined by a gamma-aminobutyric acid analogue 4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridin-3-ol and allosteric coupling: characterization using subunit-specific antibodies. 747 92

Two forms of the multisubunit gamma-aminobutyric acid (GABA)A receptor were expressed in Xenopus oocytes by injecting mRNA encoding the bovine GABAA receptor subunit cDNAs for alpha 1 beta 1 gamma 2L and alpha 3 beta 1 gamma 2L. The properties of these two combinations were examined by electrophysiological recording of GABA currents using the two-electrode voltage-clamp method. The actions of several benzodiazepine site ligands were compared in terms of their affinity for and efficacy at these two subunit combinations. Flunitrazepam potentiated control GABA responses to a maximum of 77% with alpha 1 beta 1 gamma 2L and 105% with alpha 3 beta 1 gamma 2L, with EC50 values of 29 +/- 11 nM and 23 +/- 10 nM, respectively. Flunitrazepam also produced a greater shift to the left of the GABA concentration-response curve with alpha 3 beta 1 gamma 2L than with alpha 1 beta 1 gamma 2L. Concentration-response curves for the type I benzodiazepine receptor-preferring compounds zolpidem and CL218,872 showed a selectivity for the alpha 1 beta 1 gamma 2L receptor, with respective affinity ratios 7-fold and 17-fold higher, compared with alpha 3 beta 1 gamma 2L. The inverse agonist methyl-6,7-dimethoxy-4-ethyl-beta- carboline-3-carboxylate produced a maximum inhibition of 30% with both receptor combinations and also had a higher affinity for alpha 1 beta 1 gamma 2L than alpha 3 beta 1 gamma 2L. For the first time CL218,872 and FG8205 were shown to be partial agonists of individual receptor combinations, compared with a full agonist such as flunitrazepam. The FG8205 concentration-response curve reached a maximum approximately 60% that of a full agonist with both alpha 1 beta 1 gamma 2L and alpha 3 beta 1 gamma 2L. CL218,872 reached a lower maximum efficacy with alpha 3 beta 1 gamma 2L (30%) than with alpha 1 beta 1 gamma 2L (51%), demonstrating not only that different compounds can have varying levels of partial agonist activity but also that the same compound can have differing degrees of efficacy at different receptor combinations.
Mol Pharmacol 1993 Feb
PMID:Differences in affinity and efficacy of benzodiazepine receptor ligands at recombinant gamma-aminobutyric acidA receptor subtypes. 838 10

The allosteric modulation of the progesterone metabolite 3 alpha- hydroxy-5 alpha-pregnan-20-one (DHP) on [3H]Flunitrazepam and [35S]t-butylbicyclophosphorothionate (TBPS) binding was investigated on a soluble receptor preparation. Better results in the solubilization occurred by the use of the zwitterionic detergent CHAPS with the inclusion of the phospholipid asolectin: this treatment was found suitable to study the steroidal modulation on [3H]Flunitrazepam and [35S]TBPS binding. We found that DHP was able to enhance [3H]Flunitrazepam binding in the presence of Cl- ions, while [35S]TBPS binding was inhibited by DHP. Scatchard analysis of specific [35S]TBPS and [3H]Flunitrazepam binding yielded in a single straight line both in the controls and in the presence of the hormone; DHP increased the apparent affinity of [3H]Flunitrazepam binding without altering the apparent Bmax value. In the case of [35S]TBPS, DHP decreased the apparent Bmax value whereas the Kd value remained nearly the same.
J Steroid Biochem Mol Biol 1993 Apr
PMID:3 alpha-hydroxy-5 alpha-pregnan-20-one modulation of solubilized GABA/benzodiazepine receptor complex. 838 9

Effects of conditioned emotional stimuli (CES), which induce psychological stress, on the expression of cerebral diazepam binding inhibitor (DBI) mRNA in mouse were examined using a communication box. Cerebral DBI mRNA expression significantly increased in a time-dependent manner after the application of CES. The maximal enhancement of DBI mRNA expression was observed 2 days after the application of CES, and this increase faded out over 7 days after the treatment. Flunitrazepam (1 mg/kg), an agonist for central benzodiazepine (BZD) receptors, completely abolished the CES-induced elevation of cerebral DBI contents and its mRNA expressions. These results indicate that cerebral DBI is enhanced by psychological stress, which is regulated by central BZD receptors.
Brain Res Mol Brain Res 2002 Jul 15
PMID:Psychological stress, but not physical stress, causes increase in diazepam binding inhibitor (DBI) mRNA expression in mouse brains. 1211 56