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)

MRP is a recently isolated ATP-binding cassette family transporter. We previously reported transfection studies that established that MRP confers multidrug resistance [Kruh, G. D., Chan, A., Myers, K., Gaughan, K., Miki, T. & Aaronson, S. A. (1994) Cancer Res. 54, 1649-1652] and that expression of MRP is associated with enhanced cellular efflux of lipophilic cytotoxic agents [Breuninger, L. M., Paul, S., Gaughan, K., Miki, T., Chan, A., Aaronson, S. A. & Kruh, G. D. (1995) Cancer Res. 55, 5342-5347]. To examine the biochemical mechanism by which MRP confers multidrug resistance, drug uptake experiments were performed using inside-out membrane vesicles prepared from NIH 3T3 cells transfected with an MRP expression vector. ATP-dependent transport was observed for several lipophilic cytotoxic agents including daunorubicin, etoposide, and vincristine, as well as for the glutathione conjugate leukotriene C4 (LTC4). However, only marginally increased uptake was observed for vinblastine and Taxol. Drug uptake was osmotically sensitive and saturable with regard to substrate concentration, with Km values of 6.3 microM, 4.4 microM, 4.2 microM, 35 nM, and 38 microM, for daunorubicin, etoposide, vincristine, LTC4, and ATP, respectively. The broad substrate specificity of MRP was confirmed by the observation that daunorubicin transport was competitively inhibited by reduced and oxidized glutathione, the glutathione conjugates S-(p-azidophenacyl)-glutathione (APA-SG) and S-(2,4-dinitrophenyl)glutathione (DNP-SG), arsenate, and the LTD4 antagonist MK571. This study establishes that MRP pumps unaltered lipophilic cytotoxic drugs, and suggests that this activity is an important mechanism by which the transporter confers multidrug resistance. The present study also indicates that the substrate specificity of MRP is overlapping but distinct from that of P-glycoprotein, and includes both the neutral or mildly cationic natural product cytotoxic drugs and the anionic products of glutathione conjugation. The widespread expression of MRP in tissues, combined with its ability to transport both lipophilic xenobiotics and the products of phase II detoxification, indicates that the transporter represents a widespread and remarkably versatile cellular defense mechanism.
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PMID:ATP-dependent uptake of natural product cytotoxic drugs by membrane vesicles establishes MRP as a broad specificity transporter. 955 31

MRP is a recently described ATP-binding cassette transporter that confers cellular resistance to natural product cytotoxic drugs. To examine the biochemical activity and cellular physiology of this transporter, we isolated the murine MRP homologue and analyzed its in vitro substrate specificity. Murine MRP transcript is widely expressed in tissues and encodes a protein of 1528 amino acids that is 88% identical to its human homologue. Hydropathy analysis indicated that murine and human MRP, the yeast cadmium resistance transporter and the sulfonylurea receptor share a conserved topology distinguished from P-glycoprotein and the cystic fibrosis conductance regulator by an N-terminal hydrophobic region that contains several potential transmembrane domains. Drug uptake assays performed with membrane vesicles prepared from NIH3T3 cells transfected with a murine MRP expression vector revealed ATP-dependent transport for the natural product cytotoxic drugs daunorubicin and vincristine, as well as for the glutathione S-conjugates leukotriene C4 and azidophenacyl-S-glutathione. Drug transport was osmotically sensitive and saturable with regard to drug and ATP concentrations, with K(m) values of 19 microM, 19 microM, 26 nM, 17 microM, and 77 microM for daunorubicin, vincristine, leukotriene C4, APA-SG, and ATP, respectively. Consistent with broad substrate specificity, the drug glutathione conjugate APA-SG, oxidized glutathione, the LTD4 antagonist MK571, arsenate, and genistein were competitive inhibitors of daunorubicin transport, with Ki values of 32 microM, 25 microM, 1.9 microM, 108 microM, and 23 microM, respectively. This study demonstrates that the substrate specificity of murine MRP is quite broad and includes both the neutral or mildly cationic natural product cytotoxic drugs and the anionic products of glutathione conjugation. The widespread expression pattern of murine MRP in tissues, combined with its ability to transport both lipophilic xenobiotics and the products of phase II detoxification, indicates that it represents a widespread and versatile cellular defense mechanism.
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PMID:Structure and in vitro substrate specificity of the murine multidrug resistance-associated protein. 954 10

This work presents the GnG-PK/PD-AD study-a pharmacokinetics/pharmacodynamics (PK/PD) analysis of the impact of genetic and nongenetic factors on the treatment with the antidepressant fluoxetine (FLU)-with a focus on potential biomarkers. Seventy-nine depressed patients treated with FLU were recruited and clinically characterized in the scope of the study. Clinical outcomes, including remission and antidepressant adverse effects were assessed by means of the Hamilton Depression Rating Scale and the Antidepressant Side-Effect Checklist, respectively. Patients were submitted to therapeutic drug monitoring of FLU and norfluoxetine and genotyping of the CYP2C9, CYP2C19, CYP2D6, and ABCB1 genes. A multivariate analysis was used to evaluate the impact of genetic and nongenetic factors on the drug plasma concentrations and clinical outcomes and to identify potential biomarkers. Genetically determined CYP2D6 activity was found to be a predictor of FLU and norfluoxetine concentrations (p < .05). In turn, genetic and nongenetic factors related to CYP2D6 and P-glycoprotein were found as potential biomarkers of the clinical outcomes of FLU (p < .05). Specifically, the potential of the CYP2D6 to be inhibited by drug-induced phenoconversion was associated with a higher severity of depression (p < .05). Moreover, ABCB1 TTT-haplotype was favorable to better clinical outcomes with FLU (higher likelihood of remission and lower severity of adverse effects; p < .05). The potential of the P-glycoprotein to be inhibited by drug-induced phenoconversion was also related to a worse tolerability profile (higher severity and number of adverse effects; p < .05). Lastly, the presence of nervous system comorbidities was associated with a higher severity of adverse effects and aging and the female gender with a higher severity of depression and lower probability of remission (p < .05). (PsycInfo Database Record (c) 2020 APA, all rights reserved).
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PMID:Pharmacogenetics and therapeutic drug monitoring of fluoxetine in a real-world setting: A PK/PD analysis of the influence of (non-)genetic factors. 3175 Jun 87