Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan.
Drug Metab Pharmacokinet. 2010;25(6):588-98. doi: 10.2133/dmpk.dmpk-10-rg-074. Epub 2010 Nov 12.
Recent studies indicate that various members of the organic anion transporting polypeptide (OATP) family are expressed on apical membranes of the small intestine. In the present study, we investigated possible interaction of Oatp with the PDZ protein PDZK1 in mouse small intestine, using [³H]estrone-3-sulfate (E3S) as a typical substrate. After intraduodenal administration, the level of [³H]E3S appearing in the portal vein of pdzk1 gene knockout (pdzk1(-/-)) mice was much lower than that in wild-type mice. Lower intestinal absorption of [³H]E3S in pdzk1(-/-) mice was confirmed in Ussing-type chamber experiments, which showed smaller uptake of [³H]E3S from the apical side in intestinal tissues of pdzk1(-/-) mice compared with wild-type mice. The kinetics and inhibition profile of [³H]E3S uptake in the Ussing-type chamber were similar to those in HEK293 cells stably expressing Oatp1a5, suggesting involvement of Oatp1a5 in [³H]E3S uptake. Immunoreactivity to anti-Oatp1a antibody was colocalized with PDZK1 in the small intestine of wild-type mice, whereas apical localization of Oatp1a protein was reduced in pdzk1(-/-) mice. An immunoprecipitation study revealed physical interaction of PDZK1 with Oatp1a. Thus, PDZK1 appears to act as an adaptor for Oatp1a. This is the first demonstration of a regulatory protein directly interacting with small-intestinal OATP.
最近的研究表明，有机阴离子转运多肽（OATP）家族的各种成员都表达在小肠的顶膜上。在本研究中，我们使用[³H]雌酮-3-硫酸盐（E3S）作为典型的底物，研究了 Oatp 与 PDZ 蛋白 PDZK1 在小鼠小肠中的可能相互作用。在十二指肠内给药后，pdzk1 基因敲除（pdzk1（-/-））小鼠门静脉中出现的[³H]E3S 水平远低于野生型小鼠。在 Ussing 型室实验中证实了 pdzk1（-/-）小鼠中[³H]E3S 的下肠吸收较低，这表明与野生型小鼠相比，pdzk1（-/-）小鼠肠组织从顶侧摄取[³H]E3S 的能力较小。Ussing 型室中[³H]E3S 摄取的动力学和抑制谱与稳定表达 Oatp1a5 的 HEK293 细胞中的摄取相似，表明 Oatp1a5 参与了[³H]E3S 的摄取。抗-Oatp1a 抗体的免疫反应性与野生型小鼠小肠中的 PDZK1 共定位，而 Oatp1a 蛋白的顶侧定位在 pdzk1（-/-）小鼠中减少。免疫沉淀研究显示 PDZK1 与 Oatp1a 之间存在物理相互作用。因此，PDZK1 似乎作为 Oatp1a 的衔接蛋白起作用。这是首次证明直接与小肠 OATP 相互作用的调节蛋白。
