Molecular identification and functional characterization of rat multidrug and toxin extrusion type transporter 1 as an organic cation/H+ antiporter in the kidney
Molecular identification and functional characterization of rat multidrug and toxin extrusion type transporter 1 as an organic cation/H+ antiporter in the kidney
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DOI：
10.1124/dmd.106.010876
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发表时间：
2006-11-01
影响因子：
3.9
通讯作者：
Yuasa, Hiroaki
中科院分区：
文献类型：
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作者：
Ohta, Kin-ya;Inoue, Katsuhisa;Yuasa, Hiroaki
我们克隆了大鼠多药和毒素外排型转运蛋白1（rMATE 1）的直系同源物，并对其功能进行了表征。rMATE 1的mRNA在肾脏中强烈表达，在各种组织如脑、胃、结肠、肺、肝、脾、骨骼肌和前列腺中可检测到。当在HEK 293细胞中稳定表达时，rMATE 1可以在高浓度钾离子破坏膜电位和NH 4Cl预处理降低细胞内pH的条件下介导四乙基铵（TEA）和西咪替丁的转运。当细胞外pH从5.5改变到8.5时，rMATE 1对TEA的转运在pH 7.5时最大。动力学分析表明，由rMATE 1介导的TEA和西咪替丁的转运都是饱和的，K-m分别为260 +/- 10和3.01 +/- 0.21 μ M。结果发现，西咪替丁是最有效的抑制剂rMATE 1，和许多其他有机阳离子，如1-甲基-4-苯基吡啶，阿米洛利，丙咪嗪，奎尼丁，也是有效的抑制剂。用对氯汞苯磺酸盐预处理表达rMATE 1的细胞显著降低了TEA的转运，但这种作用完全被二硫苏糖醇的后续处理逆转。这些结果表明，rMATE 1的功能性质与肾小管上皮细胞刷状缘膜中假设的有机阳离子/H+逆向转运蛋白系统的功能性质一致。因此，这些结果表明，rMATE 1是一种电中性和多特异性有机阳离子转运蛋白，由跨质子梯度提供能量，并在肾脏分泌有机阳离子（包括临床使用的阳离子药物）中发挥生理作用。
We have cloned and functionally characterized the rat ortholog of multidrug and toxin extrusion type transporter 1 ( rMATE1). The mRNA of rMATE1 was strongly expressed in kidney and detectable in the various tissues such as brain, stomach, colon, lung, liver, spleen, skeletal muscle, and prostate. When stably expressed in HEK293 cells, rMATE1 could mediate the transport of tetraethylammonium ( TEA) and cimetidine under the condition where the membrane potential was disrupted by a high concentration of potassium ion and intracellular pH was reduced by NH4Cl pretreatment. When extracellular pH was changed from 5.5 to 8.5, the transport of TEA by rMATE1 was greatest at pH 7.5. Kinetic analyses showed that the transports of TEA and cimetidine mediated by rMATE1 were both saturable with a K-m of 260 +/- 10 and 3.01 +/- 0.21 mu M, respectively. It was found that cimetidine is the most potent inhibitor of rMATE1, and many other organic cations, such as 1-methyl-4-phenylpyridinium, amiloride, imipramine, and quinidine, are also effective as inhibitors. Pretreatment of the cells expressing rMATE1 with p-chloromercuribenzene sulfonate significantly reduced TEA transport, but this effect was totally reversed by subsequent treatment with dithiothreitol. These results indicate that the functional nature of rMATE1 is consistent with that of the hypothetical organic cation/H+ antiporter system in the brush-border membrane of the renal tubular epithelial cells. Accordingly, these results suggest that rMATE1 is an electroneutral and multispecific organic cation transporter energized by the trans-proton gradient, and plays a physiological role in renal secretion of organic cations, including clinically used cationic drugs.