Organic Cation Transporter 1 (OCT1/mOct1) Is Localized in the Apical Membrane of Caco-2 Cell Monolayers and Enterocytes
Organic Cation Transporter 1 (OCT1/mOct1) Is Localized in the Apical Membrane of Caco-2 Cell Monolayers and Enterocytes
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DOI：
10.1124/mol.112.084517
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发表时间：
2013-08-01
影响因子：
3.6
通讯作者：
Thakker, Dhiren R.
中科院分区：
文献类型：
--
作者：
Han, Tianxiang (Kevin);Everett, Ruth S.;Thakker, Dhiren R.
有机阳离子转运蛋白（OCTs）是溶质载体22转运蛋白家族的成员，参与有机阳离子的吸收、分布和排泄。OCT3定位于肠细胞的顶端（AP）膜，但文献对OCT1 （mOct1）定位模棱两可，一些证据表明OCT1 （mOct1）定位于人和小鼠肠细胞的基底外侧（BL）。这与我们初步发现的OCT1在Caco-2细胞单层（一种已建立的人肠上皮模型）中的AP定位相反。因此，本研究旨在确定OCT1 （mOct1）在Caco-2细胞、人和小鼠肠细胞中的定位。使用oct1特异性底物pentamidine进行的功能研究显示，Caco-2细胞和人和小鼠肠道组织中转运蛋白介导AP而非BL摄取。在所有三种系统中，OCT1抑制使喷他脒的AP摄取减少了50%，而对BL摄取没有影响。在Caco-2细胞中，短发夹rna介导的OCT1敲低使喷他脒的AP摄取减少了50%，但没有改变BL的摄取。三种系统的免疫染色和共聚焦显微镜均证实了OCT1 （mOct1）的AP定位。我们的研究明确地表明OCT1 （mOct1）在Caco-2细胞和人和小鼠肠道中的AP膜定位。这些结果非常重要，因为它们需要重新解释先前的药物处置和药物-药物相互作用研究，这些研究的结论是假设OCT1定位于肠细胞中的BL。最重要的是，这些结果将需要修订美国和其他地方的行业监管指南，因为它已经声明OCT1在肠细胞中是基底侧定位的。
Organic cation transporters (OCTs) are members of the solute carrier 22 family of transporter proteins that are involved in absorption, distribution, and excretion of organic cations. OCT3 is localized in the apical (AP) membrane of enterocytes, but the literature is ambiguous about OCT1 (mOct1) localization, with some evidence suggesting a basolateral (BL) localization in human and mouse enterocytes. This is contrary to our preliminary findings showing AP localization of OCT1 in Caco-2 cell monolayers, an established model of human intestinal epithelium. Therefore, this study aims at determining the localization of OCT1 (mOct1) in Caco-2 cells, and human and mouse enterocytes. Functional studies using OCT1-specific substrate pentamidine showed transporter-mediated AP but not BL uptake in Caco-2 cells and human and mouse intestinal tissues. OCT1 inhibition decreased AP uptake of pentamidine by similar to 50% in all three systems with no effect on BL uptake. A short hairpin RNA-mediated OCT1 knockdown in Caco-2 cells decreased AP uptake of pentamidine by similar to 50% but did not alter BL uptake. Immunostaining and confocal microscopy in all three systems confirmed AP localization of OCT1 (mOct1). Our studies unequivocally show AP membrane localization of OCT1 (mOct1) in Caco-2 cells and human and mouse intestine. These results are highly significant as they will require reinterpretation of previous drug disposition and drug-drug interaction studies where conclusions were drawn assuming BL localization of OCT1 in enterocytes. Most importantly, these results will require revision of the regulatory guidance for industry in the United States and elsewhere because it has stated that OCT1 is basolaterally localized in enterocytes.