BOOST THE DSICOVERY OF MRP7/ABCC10 SUBSTRATES AND INHIBITORS: ESTABLISHMENT OF NEW IN VITRO AND IN SILICO MODELS

ATP-binding cassette (ABC) transporters are responsible for the efflux of structurally distinct endo- and xenobiotics energized by ATP hydrolysis. MRP7/ABCC10 belongs to the 10th member of subfamily C and responsible for mediating MDR against a series of chemotherapeutic drugs such as taxanes, epothilones, Vinca alkaloids, anthracyclines and epipodophyllotoxins. Establishment of new in silico and in vitro models for MRP7 substrates/inhibitors prediction Considering the limited knowledge of MRP7, we established a homology model based on bovine MRP1 cryo-EM models. The final model was used for protein global motion analysis and docking analysis. Before docking, potential drug binding pockets were identified and evaluated. Next, MRP7 substrates and inhibitors were docked into drug binding pockets. We found that docked inhibitors and substrates formed separate clusters, from which a substrate binding region and an inhibitor binding region were proposed. This homology protein model enables the docking analysis of potential MRP7 ligands for future studies. Moreover, we established a new SKOV3/MRP7 cell line which exhibits similar drug resistance profile as the previously established HEK/MRP7 cell line. This new cell line is valuable for MRP7 substrates and inhibitors discovery. Last but not the least, we established a novel machine learning model named Mrp7Pred for large-scale MRP7 substrates/inhibitors prediction. The model was also deployed as a web server and is freely available to users in http://www.mrp7pred.com. We successfully identified 2 substrates and 4 inhibitors from 70 FDA-approved drugs using Mrp7Pred. New synthetic agents targeting MRP7 and overcomes MRP7-medited MDR Previously, we identified two synthetic compounds, CMP25 and CP55, as potent ABCB1 and ABCG2 inhibitors. Here we found these two compounds also significantly reversed the MDR mediated by MRP7. Both compounds significantly sensitized MRP7- overexpressing HEK/MRP7 cells to paclitaxel and vincristine. Western blotting indicates that neither CMP25 nor CP55 alters MRP7 expression level. Immunofluorescence showed that the subcellular localization of MRP7 was not altered by these two compounds. However, intracellular accumulation of [3H]-paclitaxel and [3H]-vincristine were significantly increased while the efflux was significantly reduced when co- administered with CMP25 or CP55. Hydrophobic interactions were predicted as the major contributors in stabilizing the drug-protein complex via docking analysis