Bodo Adrienn, Bakos Eva, Szeri Flora, Varadi Andras, Sarkadi Balazs
National Medical Center, Institute of Haematology and Immunology, Membrane Research Group of the Hungarian Academy of Sciences.
J Biol Chem. 2003 Jun 27;278(26):23529-37. doi: 10.1074/jbc.M303515200. Epub 2003 Apr 19.
The multidrug resistance proteins MRP2 (ABCC2) and MRP3 (ABCC3) are key primary active transporters involved in anionic conjugate and drug extrusion from the human liver. The major physiological role of MRP2 is to transport conjugated metabolites into the bile canaliculus, whereas MRP3 is localized in the basolateral membrane of the hepatocytes and transports similar metabolites back to the bloodstream. Both proteins were shown to interact with a large variety of transported substrates, and earlier studies suggested that MRPs may work as co-transporters for different molecules. In the present study we expressed the human MRP2 and MRP3 proteins in insect cells and examined their transport and ATPase characteristics in isolated, inside-out membrane vesicles. We found that the primary active transport of estradiol-17-beta-d-glucuronide (E217betaG), a major product of human steroid metabolism, was differently modulated by bile acids and organic anions in the case of human MRP2 and MRP3. Active E217betaG transport by MRP2 was significantly stimulated by the organic anions indomethacin, furosemide, and probenecid and by several conjugated bile acids. In contrast, all of these agents inhibited E217betaG transport by MRP3. We found that in the case of MRP2, ATP-dependent vesicular bile acid transport was increased by E217betaG, and the results indicated an allosteric cross-stimulation, probably a co-transport of bile acids and glucuronate conjugates through this protein. There was no such stimulation of bile acid transport by MRP3. In conclusion, the different transport modulation of MRPs by bile acids and anionic drugs could play a major role in regulating physiological and pathological metabolite fluxes in the human liver.
多药耐药蛋白MRP2（ABCC2）和MRP3（ABCC3）是参与人体肝脏阴离子共轭物和药物外排的关键原发性主动转运蛋白。MRP2的主要生理作用是将共轭代谢产物转运至胆小管，而MRP3定位于肝细胞的基底外侧膜，将相似的代谢产物转运回血液。已表明这两种蛋白均能与多种转运底物相互作用，早期研究提示MRP可能作为不同分子的共转运体发挥作用。在本研究中，我们在昆虫细胞中表达了人MRP2和MRP3蛋白，并在分离的内翻膜囊泡中检测了它们的转运和ATP酶特性。我们发现，人类固醇代谢的主要产物雌二醇 - 17 - β - D - 葡萄糖醛酸苷（E217βG）的原发性主动转运在人MRP2和MRP3的情况下受到胆汁酸和有机阴离子的不同调节。吲哚美辛、呋塞米和丙磺舒等有机阴离子以及几种共轭胆汁酸可显著刺激MRP2对E217βG的主动转运。相反，所有这些试剂均抑制MRP3对E217βG的转运。我们发现，在MRP2的情况下，E217βG可增加ATP依赖性囊泡胆汁酸转运，结果表明存在变构交叉刺激，可能是胆汁酸和葡萄糖醛酸共轭物通过该蛋白的共转运。MRP3对胆汁酸转运没有这种刺激作用。总之，胆汁酸和阴离子药物对MRP的不同转运调节可能在调节人体肝脏生理和病理代谢物通量中起主要作用。
