Nunoya Kenichi, Grant Caroline E, Zhang Dawei, Cole Susan P C, Deeley Roger G
Department of Xenobiotic and Disposition, Minase Research Institute, Ono Pharmaceutical Co, Ltd, OSaka, Japan.
Drug Metab Dispos. 2003 Aug;31(8):1016-26. doi: 10.1124/dmd.31.8.1016.
Multidrug resistance protein 1 (MRP1) transports a wide range of structurally diverse conjugated and nonconjugated organic anions and some peptides, including oxidized and reduced glutathione (GSH). The protein confers resistance to certain heavy metal oxyanions and a variety of natural product-type chemotherapeutic agents. Elevated levels of MRP1 have been detected in many human tumors, and the protein is a candidate therapeutic target for drug resistance reversing agents. Previously, we have shown that human MRP1 (hMRP1) and murine MRP1 (mMRP1) differ in their substrate specificity despite a high degree of structural conservation. Since rat models are widely used in the drug discovery and development stage, we have cloned and functionally characterized rat MRP1 (rMRP1). Like mMRP1 and in contrast to hMRP1, rMRP1 confers no, or very low, resistance to anthracyclines and transports the two estrogen conjugates, 17beta-estradiol-17-(beta-d-glucuronide) (E217betaG) and estrone 3-sulfate, relatively poorly. Mutational studies combined with vesicle transport assays identified several amino acids conserved between rat and mouse, but not hMRP1, that make major contributions to these differences in substrate specificity. Despite the fact that the rodent proteins transport E217betaG poorly and the GSH-stimulated transport of estrone 3-sulfate is low compared with hMRP1, site-directed mutagenesis studies indicate that different nonconserved amino acids are involved in the low efficiency with which each of the two estrogen conjugates is transported. Our studies also suggest that although rMRP1 and mMRP1 are 95% identical in primary structure, their substrate specificities may be influenced by amino acids that are not conserved between the two rodent proteins.
多药耐药蛋白1（MRP1）可转运多种结构各异的结合型和非结合型有机阴离子以及一些肽类，包括氧化型和还原型谷胱甘肽（GSH）。该蛋白赋予细胞对某些重金属含氧阴离子和多种天然产物类化疗药物的耐药性。在许多人类肿瘤中已检测到MRP1水平升高，并且该蛋白是耐药逆转剂的候选治疗靶点。此前，我们已经表明，尽管人MRP1（hMRP1）和鼠MRP1（mMRP1）在结构上高度保守，但它们的底物特异性存在差异。由于大鼠模型在药物发现和开发阶段被广泛使用，我们克隆了大鼠MRP1（rMRP1）并对其进行了功能表征。与mMRP1一样，与hMRP1不同，rMRP1对蒽环类药物不产生或仅产生极低的耐药性，并且对两种雌激素结合物17β-雌二醇-17-（β-D-葡萄糖醛酸苷）（E217βG）和硫酸雌酮的转运相对较差。突变研究结合囊泡运输分析确定了大鼠和小鼠之间保守但hMRP1不保守的几个氨基酸，这些氨基酸对底物特异性的这些差异起主要作用。尽管啮齿动物蛋白对E217βG的转运较差，并且与hMRP1相比，GSH刺激的硫酸雌酮转运较低，但定点诱变研究表明，两种雌激素结合物各自转运效率低涉及不同的非保守氨基酸。我们的研究还表明，尽管rMRP1和mMRP1在一级结构上有95%的同一性，但它们的底物特异性可能受到这两种啮齿动物蛋白之间不保守的氨基酸的影响。
