Drug resistance and ATP-dependent conjugate transport mediated by the apical multidrug resistance protein, MRP2, permanently expressed in human and canine cells

The multidrug resistance protein MRP1 functions as an ATP-dependent conjuga te export pump and confers multidrug resistance. We cloned MRP2 (symbol ABC C2), a MRP family member localized to the apical membrane of polarized cell s. Stable expression of MRP2 in transfected human embryonic kidney (HEK-293 ) and Madin-Darby canine kidney (MDCK) cells was enhanced by inhibitors of histone deacetylase. In polarized MDCK cells, both rat and human MRP2 were sorted to the apical plasma membrane. An antibody raised against the amino terminus of rat MRP2 recognized the recombinant protein on the apical surfa ce of nonpermeabilized cells, providing direct evidence for the extracellul ar localization of the amino terminus of MRP2, ATP-dependent transport by r ecombinant human and rat MRP2 was measured with membrane vesicles from stab ly transfected cells. The K-m value of human MRP2 was 1.0 +/- 0.1 mu M for leukotriene C-4 and 7.2 +/- 0.7 mu M for 17 beta-glucuronosyl estradiol; th e K-m values of human MRP1 were 0.1 +/- 0.02 mu M for leukotriene C-4 and 1 .5 +/- 0.3 mu M for 17 beta-glucoronosyl estradiol. Thus, the conjugate-tra nsporting ATPases MRP2 and MRP1 differ not only by their domain-specific lo calization but also by their kinetic properties. Drug resistance conferred by recombinant MRP2 was studied in MDCK and HEK-293 cells using cell viabil ity assays. Expression of human and rat MRP2 enhanced the resistance of MDC K cells to etoposide 5.0-fold and 3.8-fold and to vincristine 2.3-and 6.0-f old, respectively. Buthionine sulfoximine reduced resistance to these drugs . Human MRP2 overexpressed in HEK-293 cells enhanced the resistance to etop oside (4-fold), cisplatin (10-fold), doxorubicin (7.8-fold), and epirubicin (5-fold). These results demonstrate that MRP2 confers resistance to cytoto xic drugs.