Discovery of Competitive and Noncompetitive Ligands of the Organic Cation Transporter 1 (OCT1; SLC22A1)

Organic cation transporter
1 (OCT1) plays a critical role in the
hepatocellular uptake of structurally diverse endogenous compounds
and xenobiotics. Here we identified competitive and noncompetitive
OCT1-interacting ligands in a library of 1780 prescription drugs by
combining in silico and in vitro methods. Ligands were predicted by
docking against a comparative model based on a eukaryotic homologue.
In parallel, high-throughput screening (HTS) was conducted using the
fluorescent probe substrate ASP+ in cells overexpressing
human OCT1. Thirty competitive OCT1 ligands, defined as ligands predicted
in silico as well as found by HTS, were identified. Of the 167 ligands
identified by HTS, five were predicted to potentially cause clinical
drug interactions. Finally, virtual screening of 29 332 metabolites
predicted 146 competitive OCT1 ligands, of which an endogenous neurotoxin,
1-benzyl-1,2,3,4-tetrahydroisoquinoline, was experimentally validated.
In conclusion, by combining docking and in vitro HTS, competitive
and noncompetitive ligands of OCT1 can be predicted.

有机阳离子转运体1（Organic cation transporter 1, OCT1）在结构多样的内源性化合物与外源性物质的肝细胞摄取过程中发挥关键作用。本研究通过结合计算机模拟实验（in silico）与体外实验（in vitro）方法，在包含1780种处方药的文库中筛选出可与OCT1发生竞争性和非竞争性结合的配体。研究人员基于真核同源蛋白构建的比较模型，通过分子对接预测得到候选配体；同时，以过表达人源OCT1的细胞系为模型，采用荧光探针底物ASP+开展高通量筛选（high-throughput screening, HTS）。最终鉴定出30种竞争性OCT1配体，这类配体既通过计算机模拟预测得到，也被HTS实验验证。在HTS筛选得到的167种配体中，有5种被预测可能引发临床药物相互作用。最后，本研究对29332种代谢物进行虚拟筛选，预测得到146种竞争性OCT1配体，其中一种内源性神经毒素——1-苄基-1,2,3,4-四氢异喹啉——已通过实验验证。综上，通过结合分子对接与体外HTS实验，可实现OCT1竞争性与非竞争性配体的预测。