The flexible cytoplasmic loop 3 contributes to the substrate affinity of human monocarboxylate transporters
The flexible cytoplasmic loop 3 contributes to the substrate affinity of human monocarboxylate transporters
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柔性细胞质环 3 有助于人类单羧酸转运蛋白的底物亲和力
DOI：
10.1016/j.bbamem.2017.05.014
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Iseki Ken
中科院分区：
文献类型：
--
作者：
Futagi Yuya;Sasaki Shotaro;Kobayashi Masaki;Narumi Katsuya;Furugen Ayako;Iseki Ken
人单羧酸转运蛋白 (hMCTs/SLC16As) 介导小分子量单羧酸的转运。在hMCT中，hMCT1表现出高亲和力乳酸转运和广泛的底物识别，而hMCT4表现出高度特异性底物识别和低亲和力乳酸转运，表明hMCT1和hMCT4在体内具有不同的作用。然而，转运蛋白介导的底物转运的分子机制仍然未知。本研究的目的是确定决定 hMCT1 和 hMCT4 底物选择性和亲和力的结构域。我们构建了一个嵌合体hMCT4/1，其中hMCT4的细胞质环3（TM6/7loop）区域被hMCT1的相应区域取代。爪蟾左细胞异源表达系统用于表征嵌合体的功能特征。我们已经证明 hMCT1 和 hMCT4 的底物亲和力取决于 TM6/7loop。 TM6/7loop 中的非保守 His237 残基充当底物亲和力的调节部分。相反，转运蛋白的底物选择性不依赖于TM6/7loop，表明该结构域不直接参与底物识别。我们的研究为 hMCT1 和 hMCT4 转运蛋白的结构和功能提供了重要的见解。这些发现有助于开发新型 hMCT1 和/或 hMCT4 抑制剂作为抗癌药物。
Human monocarboxylate transporters (hMCTs/SLC16As) mediate the transport of small molecular weight monocarboxylates. Among hMCTs, hMCT1 exhibits high-affinityl-lactate transport and broad substrate recognition, whereas hMCT4 shows highly specific substrate recognition and low-affinityl-lactate transport, indicating that hMCT1 and hMCT4 have different roles in the body. However, the molecular mechanism of transporter-mediated substrate transport remains unknown. The aim of this study is to identify the domain, which determines the substrate selectivity and affinity of hMCT1 and hMCT4. We constructed a chimera, hMCT4/1, in which the cytoplasmic loop 3 (TM6/7loop) region of hMCT4 was replaced by the corresponding region of hMCT1.Xenopus laevisoocyte heterologous expression system was used to characterize functional features of the chimera. We have demonstrated that the substrate affinity of hMCT1 and hMCT4 depends on the TM6/7loop. Non-conserved His237 residue in the TM6/7loop functions as a regulatory moiety of the substrate affinity. In contrast, the substrate selectivity of the transporters did not depend on the TM6/7loop, suggesting that the domain is not directly involved in substrate recognition. Our study provides important insights into the structures and functions of hMCT1 and hMCT4 transporters. These findings contribute to the development of novel hMCT1 and/or hMCT4 inhibitors as anticancer agents.