Liang Zhengxuan, You Guofeng
Department of Pharmaceutics, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Pharmaceutics. 2023 Jun 14;15(6):1725. doi: 10.3390/pharmaceutics15061725.
Organic anion transporter 3 (OAT3), at the basolateral membrane of kidney proximal tubule cells, facilitates the elimination of numerous widely used drugs. Earlier investigation from our laboratory revealed that ubiquitin conjugation to OAT3 leads to OAT3 internalization from the cell surface, followed by degradation in the proteasome. In the current study, we examined the roles of chloroquine (CQ) and hydroxychloroquine (HCQ), two well-known anti-malarial drugs, in their action as proteasome inhibitors and their effects on OAT3 ubiquitination, expression, and function. We showed that in cells treated with CQ and HCQ, the ubiquitinated OAT3 was considerably enhanced, which correlated well with a decrease in 20S proteasome activity. Furthermore, in CQ- and HCQ-treated cells, OAT3 expression and OAT3-mediated transport of estrone sulfate, a prototypical substrate, were significantly increased. Such increases in OAT3 expression and transport activity were accompanied by an increase in the maximum transport velocity and a decrease in the degradation rate of the transporter. In conclusion, this study unveiled a novel role of CQ and HCQ in enhancing OAT3 expression and transport activity by preventing the degradation of ubiquitinated OAT3 in proteasomes.
有机阴离子转运体3（OAT3）位于肾近端小管细胞的基底外侧膜，有助于清除多种广泛使用的药物。我们实验室早期的研究表明，OAT3与泛素结合会导致OAT3从细胞表面内化，随后在蛋白酶体中降解。在本研究中，我们研究了两种著名的抗疟药物氯喹（CQ）和羟氯喹（HCQ）作为蛋白酶体抑制剂的作用及其对OAT3泛素化、表达和功能的影响。我们发现，在用CQ和HCQ处理的细胞中，泛素化的OAT3显著增加，这与20S蛋白酶体活性的降低密切相关。此外，在CQ和HCQ处理的细胞中，OAT3的表达以及OAT3介导的典型底物硫酸雌酮的转运显著增加。OAT3表达和转运活性的这种增加伴随着最大转运速度的增加和转运体降解速率的降低。总之，本研究揭示了CQ和HCQ通过防止泛素化的OAT3在蛋白酶体中降解来增强OAT3表达和转运活性的新作用。
