Cloning and characterization of two human polyspecific organic cation transporters
Cloning and characterization of two human polyspecific organic cation transporters
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DOI：
10.1089/dna.1997.16.871
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发表时间：
1997-07-01
影响因子：
3.1
通讯作者：
Koepsell, H
中科院分区：
文献类型：
--
作者：
Gorboulev, V;Ulzheimer, JC;Koepsell, H
以前，我们克隆了一种大鼠多特异性转运蛋白（rOCT 1），其在肾近端小管和肝细胞中表达，并介导具有不同分子结构的有机阳离子的生电摄取，最近，克隆了一种大鼠肾脏同源转运蛋白（rOCT 2），但没有详细表征，我们报告克隆和鉴定两个同源转运蛋白从人（hOCT 1和hOCT 2）分别与rOCT 1和rOCT 2显示约80%的氨基酸同一性，北方印迹显示hOCT 1主要在肝脏中转录，而hOCT 2在肾脏中发现，原位杂交和免疫组化结果显示，hOCT 2主要在远端小管中表达，hOCT 1和hOCT 2在非洲爪蟾卵母细胞中表达后，可介导N-1-甲基烟酰胺（NMN）、四乙基铵（TEA）、和1-甲基-4-苯基吡啶鎓（MPP）。对于hOCT 2的阳离子转运，在示踪剂通量测量中测定表观K-m和K-i值。此外，用电压钳位卵母细胞进行电测量。在电压钳位的hOCT 2表达卵母细胞中，MPP、TEA、胆碱奎宁、d-筒箭毒碱、泮库溴铵和花青863，首次指出远端小管中的阳离子转运，此处hOCT 2介导阳离子重吸收的第一步。hOCT 1可能参与有机阳离子的肝脏排泄。
Previously we cloned a polyspecific transporter from rat (rOCT1) that is expressed in renal proximal tubules and hepatocytes and mediates electrogenic uptake of organic cations with different molecular structures, Recently a homologous transporter from rat kidney (rOCT2) was cloned but not characterized in detail, We report cloning and characterization of two homologous transporters from man (hOCT1 and hOCT2) displaying approximately 80% amino acid identity to rOCT1 and rOCT2, respectively, Northern blots showed that hOCT1 is mainly transcribed in liver, while hOCT2 is found in kidney, Using in situ hybridization and immunohistochemistry, expression of hOCT2 was mainly detected in the distal tubule where the transporter is localized at the luminal membrane, After expression in Xenopus laevis oocytes, hOCT1 and hOCT2 mediate tracer influx of N-1-methylnicotinamide (NMN), tetraethylammonium (TEA), and 1-methyl-4-phenylpyridinium (MPP). For cation transport by hOCT2 apparent K-m and K-i values were determined in tracer flux measurements, In addition, electrical measurements were performed with voltage-clamped oocytes, Similar to rOCT1, cation transport by hOCT2 was pH independent, electrogenic, and polyspecific; however, the cation specificity was different, In voltage-clamped hOCT2-expressing oocytes, inward currents were induced by superfusion with MPP, TEA, choline, quinine, d-tubocurarine, pancuronium, and cyanine863, Cation transport in distal tubules is indicated for the first time, Here hOCT2 mediates the first step in cation reabsorption. hOCT1 may participate in hepatic excretion of organic cations.