Miranda-Miranda Estefan, Cossío-Bayúgar Raquel, Trejo-Castro Lauro, Aguilar-Díaz Hugo
Centro Nacional de Investigación Disciplinaria en Salud Animal, Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias (INIFAP), Boulevard Cuauhnahuac No. 8534, Jiutepec 62550, Morelos, Mexico.
Centro Nacional de Servicios de Constatación en Salud Animal SENASICA-SADER, Boulevard Cuauhnahuac No. 8534, Jiutepec 62550, Morelos, Mexico.
Pathogens. 2023 Oct 18;12(10):1255. doi: 10.3390/pathogens12101255.
The expression of the carboxylesterase type B (CestB) gene is known to be induced upon exposure to the anthelmintic triclabendazole (TCBZ), leading to a substantial rise in enzyme-specific activity. Furthermore, the nucleotide sequence of the CestB gene displays variations that can potentially result in radical amino acid substitutions at the ligand binding site. These substitutions hold the potential to impact both the ligand-protein interaction and the catalytic properties of the enzyme. Thus, the objective of our study was to identify novel CestB polymorphisms in TCBZ-resistant parasites and field isolates obtained from a highly endemic region in Central Mexico. Additionally, we aimed to assess these amino acid polymorphisms using 3D modeling against the metabolically oxidized form of the anthelmintic TCBZSOX. Our goal was to observe the formation of TCBZSOX-specific binding pockets that might provide insights into the role of CestB in the mechanism of anthelmintic resistance. We identified polymorphisms in TCBZ-resistant parasites that exhibited three radical amino acid substitutions at positions 147, 215, and 263. These substitutions resulted in the formation of a TCBZSOX-affinity pocket with the potential to bind the anthelmintic drug. Furthermore, our 3D modeling analysis revealed that these amino acid substitutions also influenced the configuration of the CestB catalytic site, leading to alterations in the enzyme's interaction with chromogenic carboxylic ester substrates and potentially affecting its catalytic properties. However, it is important to note that the TCBZSOX-binding pocket, while significant for drug binding, was located separate from the enzyme's catalytic site, rendering enzymatic hydrolysis of TCBZSOX impossible. Nonetheless, the observed increased affinity for the anthelmintic may provide an explanation for a drug sequestration type of anthelmintic resistance. These findings lay the groundwork for the future development of a molecular diagnostic tool to identify anthelmintic resistance in .
已知在接触驱虫药三氯苯达唑（TCBZ）后，B型羧酸酯酶（CestB）基因的表达会被诱导，导致酶特异性活性大幅上升。此外，CestB基因的核苷酸序列存在变异，这可能会在配体结合位点导致根本性的氨基酸替换。这些替换有可能影响配体与蛋白质的相互作用以及酶的催化特性。因此，我们研究的目的是在从墨西哥中部一个高度流行地区获得的TCBZ抗性寄生虫和野外分离株中鉴定新的CestB多态性。此外，我们旨在使用针对驱虫药TCBZSOX代谢氧化形式的三维建模来评估这些氨基酸多态性。我们的目标是观察TCBZSOX特异性结合口袋的形成，这可能有助于深入了解CestB在驱虫抗性机制中的作用。我们在TCBZ抗性寄生虫中鉴定出多态性，这些寄生虫在第147、215和263位表现出三个根本性的氨基酸替换。这些替换导致形成了一个具有结合驱虫药潜力的TCBZSOX亲和口袋。此外，我们的三维建模分析表明，这些氨基酸替换还影响了CestB催化位点的构型，导致酶与显色羧酸酯底物的相互作用发生改变，并可能影响其催化特性。然而，需要注意的是，TCBZSOX结合口袋虽然对药物结合很重要，但它与酶的催化位点是分开的，使得TCBZSOX的酶促水解成为不可能。尽管如此，观察到的对驱虫药亲和力的增加可能为一种药物隔离型驱虫抗性提供解释。这些发现为未来开发一种分子诊断工具奠定了基础，以鉴定[此处原文缺失相关内容]中的驱虫抗性。
