Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously demonstrated that multidrug-resistant cells have a lower content of lysosomal enzymes, a consequence of an increased rate of secretion. The question was therefore to know whether an intact functional P-glycoprotein was necessary for expression of this property. Control NIH3T3 and mdr1-gene-transfected cells (pHaMDR1) were used together with 2 variants either lacking 23 amino acids at the carboxyl terminal (pHaMDRC 23) or in which 4 extra amino acids are inserted (pHaMDRBL2). Transfected and variant cells exhibited reduced uptake of [3H]-vinblastine and [3H]-daunomycin, a finding consistent with their drug resistance. By contrast, only pHaMDR1 cells had a reduced level of N-acetyl glucosaminidase that paralleled an increased rate of secretion of the same enzyme. The mutant cells secreted lysosomal enzyme at the same rate and had the same intracellular lysosomal enzyme content as NIH3T3 cells. Abnormal behavior of lysosomal enzymes in multidrug-resistant cells therefore seemed to require an intact P-glycoprotein molecule. Although sequestration in lysosomes and then secretion of drugs may possibly contribute to protection, it would not be an essential component of multidrug resistance.
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PMID:The structure of P-glycoprotein and the secretion of lysosomal enzymes in multidrug-resistant cells. 780 88

Oseltamivir is an ethyl ester prodrug of [3R,4R,5S]-4-acetamido-5-amino-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylate phosphate (Ro 64-0802), the anti-influenza drug. Abnormal behavior has been suspected to be associated with oseltamivir medication in Japan. The purpose of the present study is to examine the involvement of transporters in the brain distribution of oseltamivir and its active form Ro 64-0802 across the blood-brain barrier (BBB). The brain-to-plasma concentration ratio (K(p,brain)) of oseltamivir after i.v. infusion of oseltamivir in FVB mice was increased by pretreatment with N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918), a dual inhibitor for P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), whereas that of Ro 64-0802 was only slightly increased. Furthermore, the distribution volume of Ro 64-0802 following i.v. administration of Ro 64-0802 in the brain was similar to the capillary volume, suggesting its minimal distribution. The K(p,brain) value of oseltamivir in multidrug-resistant (Mdr) 1a/1b P-gp knockout mice was 5.5-fold higher than that in wild-type mice and comparable with that obtained by pretreatment with GF120918, whereas it was unchanged in Bcrp knockout mice. The K(p,brain) value of oseltamivir was significantly higher in newborn rats, which is in good agreement with the ontogenetic expression profile of P-gp. Intracellular accumulation of oseltamivir was lower in human and mouse P-gp-expressing cells, which was reversed by P-gp inhibitor valspodar (PSC833). These results suggest that P-gp limits the brain uptake of oseltamivir at the BBB and that Ro 64-0802 itself barely crosses the BBB. However, it may be possible that Ro 64-0802 is formed in the brain from the oseltamivir, considering the presence of carboxylesterase in the brain endothelial cells.
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PMID:P-glycoprotein restricts the penetration of oseltamivir across the blood-brain barrier. 1803 6