Structural insights into the differences among lactisole derivatives in inhibitory mechanisms against the human sweet taste receptor
Structural insights into the differences among lactisole derivatives in inhibitory mechanisms against the human sweet taste receptor
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DOI：
10.1371/journal.pone.0213552
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发表时间：
2019-03-18
期刊：
影响因子：
3.7
通讯作者：
Misaka, Takumi
中科院分区：
文献类型：
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作者：
Nakagita, Tomoya;Ishida, Akiko;Misaka, Takumi
乳交酯是人类甜味受体的抑制剂，具有2-苯氧基丙酸骨架，并已显示与受体的T1 R3亚基（T1 R3-TMD）的跨膜结构域相互作用。另一种抑制剂，2，4-DP，与lactisole具有相同的分子骨架，经证实其抑制活性比lactisole强约10倍;然而，其对受体的抑制机制的结构基础仍有待阐明。代谢型谷氨酸受体的TMD的晶体结构，其沿着T1 R一起被分类为C类G蛋白偶联受体，最近已经被报道，并且使得有可能创建T1 R 3-TMD的精确结构模型。在这项研究中，甜味抑制的详细结构机制，其特征在于通过比较的作用lactisole T1 R3-TMD与2，4-DP。我们首先使用表达突变甜味受体的培养细胞进行了一系列实验，并检查了与这些抑制剂的相互作用。根据结果，我们接下来进行对接模拟，然后应用基于分子动力学的能量最小化。我们的分析清楚地表明，乳糖醇和2，4-DP的（S）-异构体与T1 R3-TMD中相同的7个残基相互作用，并且这些抑制剂的抑制效力主要是由于通过T1 R3-TMD配体口袋垂直维度中的羧基介导的稳定相互作用。此外，2，4-DP还参与了由邻氯基介导的疏水相互作用，这种相互作用可能是2，4-DP具有更高抑制效力的主要原因。
Lactisole, an inhibitor of the human sweet taste receptor, has a 2-phenoxypropionic acid skeleton and has been shown to interact with the transmembrane domain of the T1R3 subunit (T1R3-TMD) of the receptor. Another inhibitor, 2,4-DP, which shares the same molecular skeleton as lactisole, was confirmed to be approximately 10-fold more potent in its inhibitory activity than lactisole; however the structural basis of their inhibitory mechanisms against the receptor remains to be elucidated. Crystal structures of the TMD of metabotropic glutamate receptors, which along with T1Rs are categorized as class C G-protein coupled receptors, have recently been reported and made it possible to create an accurate structural model for T1R3-TMD. In this study, the detailed structural mechanism underlying sweet taste inhibition was characterized by comparing the action of lactisole on T1R3-TMD with that of 2,4-DP. We first performed a series of experiments using cultured cells expressing the sweet taste receptor with mutations and examined the interactions with these inhibitors. Based on the results, we next performed docking simulations and then applied molecular dynamics-based energy minimization. Our analyses clearly revealed that the (S)-isomers of both lactisole and 2,4-DP, interacted with the same seven residues in T1R3-TMD and that the inhibitory potencies of those inhibitors were mainly due to stabilizing interactions mediated via their carboxyl groups in the vertical dimension of the ligand pocket of T1R3-TMD. In addition, 2,4-DP engaged in a hydrophobic interaction mediated by its o-Cl group, and this interaction may be chiefly responsible for the higher inhibitory potency of 2,4-DP.