Noguchi Tomohiro, Ren Xiao-Qin, Aoki Shunji, Igarashi Yoshinobu, Che Xiao-Fang, Nakajima Yuichi, Takahashi Homare, Mitsuo Ryoichi, Tsujikawa Kazutake, Sumizawa Tomoyuki, Haraguchi Misako, Kobayashi Motomasa, Goto Susumu, Kanehisa Minoru, Aikou Takashi, Akiyama Shin-ichi, Furukawa Tatsuhiko
Department Molecular Oncology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima 890-8544, Japan.
Biochem Pharmacol. 2005 Oct 1;70(7):1056-65. doi: 10.1016/j.bcp.2005.06.025.
Multidrug resistance protein 1 (MRP1) is an ATP-binding cassette transporter that confers multidrug resistance on tumor cells. Much convincing evidence has accumulated that MRP1 transports most substances in a GSH-dependent manner. On the other hand, several reports have revealed that MRP1 can transport some substrates independently of GSH; however, the importance of GSH-independent transport activity is not well established and the mechanistic differences between GSH-dependent and -independent transport by MRP1 are unclear. We previously demonstrated that the amino acids W261 and K267 in the L0 region of MRP1 were important for leukotriene C4 (LTC4) transport activity of MRP1 and for GSH-dependent photolabeling of MRP1 with azidophenyl agosterol-A (azidoAG-A). In this paper, we further tested the effect of W222L, W223L and R230A mutations in MRP1, designated dmL0MRP1, on MRP1 transport activity. SN-38 is an active metabolic form of CPT-11 that is one of the most promising anti-cancer drugs. Membrane vesicles prepared from cells expressing dmL0MRP1 could transport SN-38, but not LTC4 or estradiol-17 (beta-D-glucuronate), and could not be photolabeled with azidoAG-A. These data suggested that SN-38 was transported by a different mechanism than that of GSH-dependent transport. Understanding the GSH-independent transport mechanism of MRP1, and identification of drugs that are transported by this mechanism, will be critical for combating MRP1-mediated drug resistance. We performed a pairwise comparison of compounds that are transported by MRP1 in a GSH-dependent or -independent manner. These data indicated that it may be possible to predict compounds that are transported by MRP1 in a GSH-independent manner.
多药耐药蛋白1（MRP1）是一种ATP结合盒转运蛋白，可赋予肿瘤细胞多药耐药性。已有大量令人信服的证据表明，MRP1以谷胱甘肽（GSH）依赖的方式转运大多数物质。另一方面，一些报告显示MRP1可以独立于GSH转运某些底物；然而，GSH非依赖性转运活性的重要性尚未完全确立，且MRP1的GSH依赖性和非依赖性转运之间的机制差异尚不清楚。我们之前证明，MRP1的L0区域中的氨基酸W261和K267对MRP1的白三烯C4（LTC4）转运活性以及MRP1与叠氮苯阿戈甾醇-A（azidoAG-A）的GSH依赖性光标记很重要。在本文中，我们进一步测试了MRP1中W222L、W223L和R230A突变体（称为dmL0MRP1）对MRP1转运活性的影响。SN-38是CPT-11的活性代谢形式，CPT-11是最有前途的抗癌药物之一。从表达dmL0MRP1的细胞制备的膜囊泡可以转运SN-38，但不能转运LTC4或雌二醇-17（β-D-葡萄糖醛酸），并且不能被azidoAG-A光标记。这些数据表明，SN-38的转运机制与GSH依赖性转运不同。了解MRP1的GSH非依赖性转运机制，并鉴定通过该机制转运的药物，对于对抗MRP1介导的耐药性至关重要。我们对以GSH依赖性或非依赖性方式被MRP1转运化合物进行了成对比较。这些数据表明，有可能预测以GSH非依赖性方式被MRP1转运的化合物。
