Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Opioid binding in subcellular fractions from neurohybrid cells was assessed using two models of up-regulation. Homologous up-regulation was achieved by treating NG108-15 cells with the opioid antagonist naltrexone. Na butyrate was added to NCB-20 cell cultures to affect heterologous up-regulation. In both paradigms light and heavy membranes were resolved by concanavalin A (con A) pretreatment of cells followed by density centrifugation. [3H][D-Ala2,D-Leu5]enkephalin (DADLE) and [3H]diprenorphine Bmax values for these fractions increased without changes in affinity. In contrast to 48 h of antagonist treatment, 5 min of exposure to naltrexone down-regulated heavy membrane delta sites. Under both conditions of up-regulation, inhibition of LM [3H]DADLE specific binding by 5'-guanylylimidodiphosphate was enhanced suggesting greater receptor coupling to guanine nucleotide binding regulatory proteins. Although attenuated by addition of cycloheximide, [3H]DADLE binding to total homogenates increased upon naltrexone treatment of NG108-15 cells. Heavy membrane Bmax values were also augmented in the presence of cycloheximide and naltrexone for 48 h. Activities of beta-glucuronidase and beta-hexoseaminidase were diminished in total homogenates and subcellular fractions from naltrexone-treated cells, suggesting an opioid-induced alteration in lysosomal enzyme trafficking. Comparable receptor down- and up-regulation and attenuation of lysosomal enzyme activity were elicited by the delta-selective opioid peptide antagonist (allyl)2 Tyr-Aib-Aib-Phe-Leu-OH. These results suggest that homologous up-regulation entails initial down-regulation and blockade of receptor degradation.
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PMID:Up-regulation of delta opioid receptors in neuroblastoma hybrid cells: evidence for differences in the mechanisms of action of sodium butyrate and naltrexone. 165 25

A subclone of NG108-15 neuroblastoma-glioma hybrid cells was used to study the intracellular distribution of opioid receptors. Subcellular organelles were separated on self-generating Percoll-sucrose gradients and the enzymes beta-glucuronidase, galactosyltransferase, 5'-nucleotidase, and glucose-6-phosphatase were used as markers to localize the various structures. Analysis of the receptor distribution from untreated cells shows that the plasma membranes contained the highest receptor density, but a significant portion of the opioid binding sites was unevenly distributed between the lysosomes, microsomes, and Golgi elements. The enzyme markers indicated that appearance of opioid receptors in these intracellular structures does not result merely from contamination with plasma membranes. About 11% of the receptors appeared in a fraction lighter than plasma membranes. The antilysosomal agent chloroquine altered the intracellular compartmentation of the receptors, possibly by blocking their translocation in the cells. Leu-enkephalin induced time-dependent loss of receptors from all four intracellular compartments examined, but a kinetic analysis showed that the rate of receptor loss in these fractions was not identical. Thus, the percent of receptors appearing in the lysosomal fraction that could still bind [3H]D-Ala2-D-Leu5-enkephalin in vitro was increased on treatment with Leu-enkephalin. As an additional approach to follow the intracellular fate of the receptors, cells were labeled with [3H]diprenorphine, chased with various unlabeled opiates, and the distribution of 3H-ligand-receptors in the cells was monitored. Leu-enkephalin and etorphine altered the distribution of receptor-bound [3H]diprenorphine between the plasma membranes, lysosomes, and Golgi elements, whereas morphine had no such effect. The study sheds light on the role of intracellular structures in the metabolism of opioid receptors in untreated and opioid-treated cells.
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PMID:Subcellular compartmentation of opioid receptors: modulation by enkephalin and alkaloids. 300 5