Functional characterization of rat organic anion transporter 5 (Slc22a19) at the apical membrane of renal proximal tubules
Functional characterization of rat organic anion transporter 5 (Slc22a19) at the apical membrane of renal proximal tubules
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DOI：
10.1124/jpet.105.088583
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发表时间：
2005-11-01
影响因子：
3.5
通讯作者：
Anzai, N
中科院分区：
文献类型：
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作者：
Anzai, N;Jutabha, P;Anzai, N
据报道，有机阴离子转运蛋白 (OAT) 家族的新成员 Oat5 (Slc22a19) 可转运天然存在的霉菌毒素赭曲霉毒素 A (OTA)。然而，其内源底物和驱动力以及生理功能尚未确定。在此，我们报告了大鼠 Oat5 (rOat5) 的功能特征及其肾内分布和膜定位。当在非洲爪蟾卵母细胞中表达时，除了OTA之外，rOat5还以不依赖于钠的方式介导类固醇硫酸盐缀合物的转运，例如雌酮3-硫酸盐（E1S；K-m=18.9+/-3.9μM）和硫酸脱氢表雄酮（K-m=2.3+/-0.2μM）。 rOat5 介导的 E1S 转运受到四碳 (C4) 二羧酸琥珀酸和较长二羧酸 (C7-C9) 的强烈抑制。通过 rOat5 对 [3H] E1S 的摄取受到琥珀酸的显着反式刺激，并且 [C-14] 琥珀酸的流出受到 E 1 S 的显着反式刺激。在稳定表达 rOat5 (S-2 rOat5) 的细胞中也检测到预加载的琥珀酸对 E 1 S 摄取的类似反式刺激作用。 rOat5 与化学异质阴离子化合物相互作用。 rOat5 介导的 E 1 S 转运可被几种硫酸盐结合物抑制，例如 4-甲基伞形基硫酸盐和 β-雌二醇硫酸盐，但不能被葡萄糖醛酸结合物抑制。免疫组织化学研究表明，rOat5 位于皮质髓质区域肾近曲小管的顶膜。 rOat5 mRNA 在近曲小管的晚期段（S-2 和 S-3）中表达。这些结果表明，rOat5 是肾脏有机阴离子/二羧酸盐交换剂，并且在生理条件下，可能作为由二羧酸盐向外梯度驱动的近端小管中有机阴离子的顶端重吸收途径。
A novel member of the organic anion transporter (OAT) family, Oat5 (Slc22a19), has been reported to transport a naturally occurring mycotoxin, ochratoxin A (OTA). However, neither its endogenous substrate and driving force nor physiological functions have been determined. Herein, we report the functional characterization of rat Oat5 (rOat5), as well as its intrarenal distribution and membrane localization. When expressed in Xenopus laevis oocytes, rOat5 mediated the transport of sulfate conjugates of steroids such as estrone-3-sulfate (E1S; K-m = 18.9 +/- 3.9 mu M) and dehydroepiandrosterone sulfate (K-m = 2.3 +/- 0.2 mu M) in a sodium-independent manner, in addition to OTA. The rOat5-mediated E1S transport was strongly inhibited by four-carbon (C4) dicarboxylate succinate and longer dicarboxylates (C7-C9). The uptake of [3H] E1S via rOat5 was significantly trans-stimulated by succinate, and the efflux of [C-14] succinate was significantly trans-stimulated by E 1 S. A similar trans-stimulatory effect of preloaded succinate on E 1 S uptake was also detected in cells stably expressing rOat5 (S-2 rOat5). rOat5 interacted with chemically heterogenous anionic compounds. The rOat5-mediated E 1 S transport was inhibited by several sulfate conjugates, such as 4-methylumbelliferyl sulfate and beta-estradiol sulfate, but not by glucuronide conjugates. An immunohistochemical study showed that rOat5 was localized at the apical membrane of renal proximal tubules in the corticomedullary region. rOat5 mRNA was expressed in the late segments (S-2 and S-3) of proximal tubules. These results indicate that rOat5 is renal organic anion/dicarboxylates exchanger and, under physiological conditions, may function as an apical reabsorptive pathway for organic anions in proximal tubules driven by an outward gradient of dicarboxylates.