Tamsulosin ameliorates bone loss by inhibiting the release of Cl <sup>−</sup> through wedging into an allosteric site of TMEM16A
Abstract
TMEM16A, a key calcium-activated chloride channel, is crucial for many physiological and pathological processes such as cancer, hypertension, and osteoporosis, etc. However, the regulatory mechanism of TMEM16A is poorly understood, limiting the discovery of effective modulators. Here, we unveil an allosteric gating mechanism by presenting a high-resolution cryo-EM structure of TMEM16A in complex with a channel inhibitor that we identified, Tamsulosin, which is resolved at 2.93 Å. Tamsulosin wedges itself into a pocket within the extracellular domain of TMEM16A, surrounded by α1-α2, α5-α6, and α9-α10 loops. This binding stabilizes a transient preopen conformation of TMEM16A, which is activated by Ca 2+ ions while still preserving a closed pore to prevent Cl − permeation. Validation of this binding site through computational, electrophysiological, and functional experiments, along with site-directed mutagenesis, confirmed the pivotal roles of the pocket-lining residues R605 and E624 on α5-α6 loop in modulating Tamsulosin binding and pore activity. Tamsulosin induces significant positional shifts in extracellular loops, particularly the α5-α6 loop, which moves toward the extracellular exit of the pore, leading to noticeable structural rearrangements in pore-lining helices. The hinges induced by P595 in α5 and G711 in α7 introduce flexibility to the transmembrane helices, orienting Y593 to collaborate with I641 in effectively gating the preopening pore. Notably, Tamsulosin demonstrates significant antiosteoporotic effects by inhibiting TMEM16A, suggesting potential for its repurposing in new therapeutic indications. Our study not only enhances our understanding of the gating mechanism of TMEM16A inhibition but also facilitates structure-based drug design targeting TMEM16A.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (20)
Shiliang Li
Beijing National Laboratory for Condensed Matter Physics
Weijia Sun
National Key Laboratory of Space Medicine, China Astronaut Research and Training Center
Shuang Li
Lili Zhu
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology
Shuai Guo
Department of Chemistry
Jiaqi He
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology
Yuheng Li
State Key Laboratory of Structural Chemistry
Chaoquan Tian
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology
Zhenjiang Zhao
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology
Tao Yu
Jianwei Li
Macao Institute of Materials Science and Engineering (MIMSE), Faculty of Innovation Engineering, Macau University of Science and Technology, Taipa, 999078 Macao, China
Yiqing Zhang
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology
Youlong Hai
Department of Urology, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine
Jiawen Wang
Institute of Functional Nano & Soft Materials (FUNSOM)
Yongjun Zheng
Jiangsu Engineering Laboratory of Smart Carbon-Rich Materials and Device, Jiangsu Province Hi-Tech Key Laboratory for Bio-Medical Research, School of Chemistry and Chemical Engineering, Medical School
Rui Wang
Xiaoyong Hu
Department of Urology, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine
Shukuan Ling
Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine Vision and Brain Health)
Honglin Li
Innovation Center for AI and Drug Discovery, School of Pharmacy, East China Normal University
Yingxian Li
National Key Laboratory of Space Medicine, China Astronaut Research and Training Center