OATP2B1 belongs to a highly conserved organic anion transporting polypeptide (OATP) family of transporters, involved in the cellular uptake of both endogenous and exogenous compounds. The reported substrates of human OATP2B1 include steroid conjugates, bile salts, and thyroid hormones, as well as pharmaceuticals. Human OATP2B1 has orthologous genes in other vertebrate species, including zebrafish (Danio rerio), a widely used model organism in biomedical and environmental research. Our previous studies showed that zebrafish Oatp2b1 was phylogenetically closest to mammalian OATP2B1/Oatp2b1 and that it shares a similar tissue expression pattern. In this study, we aimed at discovering whether zebrafish Oatp2b1 could be a functional ortholog of human and rodent OATP2B1. To test this hypothesis, our primary goal was to obtain the first in vitro and in silico insights related to the structure and potential substrate preferences of zebrafish Oatp2b1. We generated cells transiently and stably transfected with zebrafish Oatp2b1 cloned from zebrafish liver, constructed an Oatp2b1 homology model, developed transport activity assays with model fluorescent substrate Lucifer yellow, and finally utilized this assay to analyze the interaction of zebrafish Oatp2b1 with both physiological and xenobiotic substances. Apart from structure similarities, our data revealed the strongest interaction of zebrafish Oatp2b1 with bile acids, steroid sulfates, thyroid hormones, and bilirubin, as well as xenobiotics bromosulfophthalein and sulfasalazine, which indicates its functional orthology with human OATP2B1.

OATP2B1 属于高度保守的有机阴离子转运多肽 (OATP) 转运蛋白家族，参与细胞摄取内源性和外源性化合物。已报道的人 OATP2B1 底物包括类固醇结合物、胆汁盐和甲状腺激素，以及药物。人类OATP2B1在其他脊椎动物物种中具有直系同源基因，包括斑马鱼 ( Danio rerio)，一种在生物医学和环境研究中广泛使用的模式生物。我们之前的研究表明，斑马鱼 Oatp2b1 在系统发育上最接近哺乳动物 OATP2B1/Oatp2b1，并且它具有相似的组织表达模式。在这项研究中，我们旨在发现斑马鱼 Oatp2b1 是否可以成为人类和啮齿动物 OATP2B1 的功能直系同源物。为了验证这一假设，我们的主要目标是获得与斑马鱼 Oatp2b1 的结构和潜在底物偏好相关的第一个体外和计算机洞察力。我们用从斑马鱼肝脏中克隆的斑马鱼 Oatp2b1 瞬时稳定转染了细胞，构建了 Oatp2b1 同源模型，使用模型荧光底物路西法黄开发了转运活性测定，最后利用该测定分析斑马鱼 Oatp2b1 与生理和异生物质的相互作用。除了结构相似性外，我们的数据还揭示了斑马鱼 Oatp2b1 与胆汁酸、类固醇硫酸盐、甲状腺激素和胆红素以及异生物质溴磺酞和柳氮磺胺吡啶的最强相互作用，这表明其与人类 OATP2B1 的功能同源性。