Cloning and functional expression of a human liver organic cation transporter
Cloning and functional expression of a human liver organic cation transporter
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DOI：
10.1124/mol.51.6.913
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发表时间：
1997-06-01
影响因子：
3.6
通讯作者：
Giacomini, KM
中科院分区：
文献类型：
--
作者：
Zhang, L;Dresser, MJ;Giacomini, KM
肝脏中的多特异性有机阳离子转运蛋白介导多种内源性胺和外源物质的消除。与我们对大鼠肝脏中有机阳离子转运机制的理解相反，人们对人类肝脏中有机阳离子转运机制知之甚少。我们报告了第一个来自肝脏的人类多特异性有机阳离子转运蛋白（hOCT1）的克隆、测序和功能表征。 hOCT1（554 个氨基酸）与先前克隆的大鼠有机阳离子转运蛋白 rOCT1 [Nature (Lend.) 372:549-552 (1994)] 78% 相同。在注射 hOCT1 cRNA 的非洲爪蟾卵母细胞中，有机阳离子 H-3-1-甲基-4-苯基吡啶鎓 (H-3-MPP+) 的特异性摄取比注射水的卵母细胞显着增强（8 倍）。 H-3-MPP+ 的吸收是饱和的（K-m = 14.6 +/- 4.39 mu M）并且对膜电位敏感。小的一价有机阳离子（例如四乙铵和 N-1-甲基烟酰胺）和较大的有机阳离子（例如维库溴铵和癸鎓-22）都会抑制 H-3-MPP+ 的摄取。此外，胆汁酸牛磺胆酸盐抑制表达 hOCT1 的卵母细胞对 H-3-MPP+ 的摄取。 Northern分析证明hOCT1的mRNA转录物主要在人肝脏中表达，而rOCT1的mRNA转录物在大鼠肾、肝、肠和结肠中发现[Nature(Lend.)372：549-552(1994)]。与rOCT1相比，hOCT1在动力学特征和组织分布方面表现出显着差异。 hOCT1的功能表达将为阐明人肝脏中有机阳离子转运机制以及了解药物的处置和肝毒性机制提供有力的工具。
Polyspecific organic cation transporters in the liver mediate the elimination of a wide array of endogenous amines and xenobiotics. In contrast to our understanding of the mechanisms of organic cation transport in rat liver, little is known about the mechanisms of organic cation transport in the human liver. We report the cloning, sequencing, and functional characterization of the first human polyspecific organic cation transporter from liver (hOCT1). hOCT1 (554 amino acids) is 78% identical to the previously cloned organic cation transporter from rat, rOCT1 [Nature (Lend.) 372:549-552 (1994)]. In Xenopus laevis oocytes injected with the cRNA of hOCT1, the specific uptake of the organic cation H-3-1-methyl-4-phenylpyridinium (H-3-MPP+) was significantly enhanced (8-fold) over that in water-injected oocytes. Uptake of H-3-MPP+ was saturable (K-m = 14.6 +/- 4.39 mu M) and sensitive to membrane potential. Both small monovalent organic cations such as tetraethylammonium and N-1-methylnicotinamide and bulkier organic cations (e.g., vecuronium and decynium-22) inhibited the uptake of H-3-MPP+. In addition, the bile acid taurocholate inhibited the uptake of H-3-MPP+ in oocytes expressing hOCT1. Northern analysis demonstrated that the mRNA transcript of hOCT1 is expressed primarily in the human liver, whereas the mRNA transcript of rOCT1 is found in rat kidney, liver, intestine, and colon [Nature (Lend.) 372:549-552 (1994)]. In comparison to rOCT1, hOCT1 exhibits notable differences in its kinetic characteristics and tissue distribution. The functional expression of hOCT1 will provide a powerful tool for elucidation of the mechanisms of organic cation transport in the human liver and understanding of the mechanisms involved in the disposition and hepatotoxicity of drugs.