Center for Cellular Imaging and NanoAnalytics (C-CINA), Biozentrum, University of Basel, Mattenstrasse 26, 4058 Basel, Switzerland.
Institute of Molecular Biology and Biophysics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland.
Nature. 2017 Jun 22;546(7659):504-509. doi: 10.1038/nature22345. Epub 2017 May 29.
ABCG2 is a constitutively expressed ATP-binding cassette (ABC) transporter that protects many tissues against xenobiotic molecules. Its activity affects the pharmacokinetics of commonly used drugs and limits the delivery of therapeutics into tumour cells, thus contributing to multidrug resistance. Here we present the structure of human ABCG2 determined by cryo-electron microscopy, providing the first high-resolution insight into a human multidrug transporter. We visualize ABCG2 in complex with two antigen-binding fragments of the human-specific, inhibitory antibody 5D3 that recognizes extracellular loops of the transporter. We observe two cholesterol molecules bound in the multidrug-binding pocket that is located in a central, hydrophobic, inward-facing translocation pathway between the transmembrane domains. Combined with functional in vitro analyses, our results suggest a multidrug recognition and transport mechanism of ABCG2, rationalize disease-causing single nucleotide polymorphisms and the allosteric inhibition by the 5D3 antibody, and provide the structural basis of cholesterol recognition by other G-subfamily ABC transporters.
ABCG2 是一种组成型表达的三磷酸腺苷（ATP）结合盒（ABC）转运体，可保护许多组织免受外源性分子的侵害。其活性会影响常用药物的药代动力学，并限制治疗药物进入肿瘤细胞，从而导致多药耐药。本文通过冷冻电镜确定了人源 ABCG2 的结构，首次提供了对人源多药转运体的高分辨率见解。我们观察到 ABCG2 与两种人源特异性抑制性抗体 5D3 的抗原结合片段复合物，该抗体识别转运体的细胞外环。我们观察到两个胆固醇分子结合在位于跨膜结构域之间的中央、疏水性、内向移位途径中的多药物结合口袋中。与体外功能分析相结合，我们的结果表明了 ABCG2 的多药物识别和转运机制，合理解释了导致疾病的单核苷酸多态性和 5D3 抗体的别构抑制，并为其他 G 亚家族 ABC 转运体识别胆固醇提供了结构基础。
