z-bio 2025-03-25 262

　　Schematic diagram of the conformational gating and regulatory mechanism of Tamsulosin combined with TMEM16A extracellular domain hidden pocket

　　With the support of the National Natural Science Foundation of China projects (approval numbers: 82192880, 82192882) and other grants, the research teams led by Li Yingxian from the China Astronaut Research and Training Center, Professor Li Honglin from East China Normal University, and Ling Shukuan from the Oujiang Laboratory have made progress in the study of new uses of old drugs and their mechanisms of action. The research findings, titled "Tamsulosin Amelirates bone loss by inhibiting the release of Cl ⁻ through wedging into a novel allosteric site of TMEM16A", were published online on December 31, 2024 in the Proceedings of the National Academy of Sciences. Paper link: https://www.pnas.org/doi/10.1073/pnas.2407493121 .

　　With the acceleration of global population aging, osteoporosis is becoming an increasingly severe public health problem. Transmembrane protein 16A (TMEM16A) is a calcium activated chloride ion channel, but due to insufficient understanding of its regulatory mechanism, the development of effective inhibitors still faces significant challenges.

　　The research team used the self-developed molecular three-dimensional similarity method SHAFTS (SHApe FeaTrue Similarity, a mixed computing method that simultaneously considers molecular shape feature similarity) and found that the drug Tamsulosin, which is used to treat benign prostatic hyperplasia, exhibits good inhibitory activity against TMEM16A (IC50=7.22 μ M). Subsequently, the complex structure of TMEM16A and Tamsulosin was analyzed using cryo electron microscopy technology (Protein Database (PDB) ID: Using 8XLR with a resolution of 2.93 Å, it was found that Tamsulosin wedged into a novel implicit pocket of the extracellular domain of TMEM16A, stabilizing the pre opening transient conformation of TMEM16A under Ca2+activation, preventing pore opening and Cl - permeation. The key roles of arginine 605, glutamic acid 624, tyrosine 593, and isoleucine 641 in regulating Tamsulosin binding and pore conformation and activity were further validated through the comprehensive application of molecular dynamics simulation, electrophysiology, point mutation, and functional experiments. Tamsulosin effectively inhibits TMEM16A current, suppresses osteoclast differentiation, reduces the expression of key osteoclast marker genes, and inhibits bone resorption by regulating Cl - concentration and signaling pathways such as Syk Btk PLC γ 2 and CaMKIV-CREB-NFATc1. In a mouse model of osteoporosis induced by ovariectomy, Tamsulosin significantly improved bone density and structure, reduced bone resorption marker CTX-1, and osteoclast gene expression (Figure).

　　This study discovered a new use of the old drug Tamsulosin through computational simulation combined with pharmacology, and confirmed through structural biology methods that Tamsulosin wedges into the target TMEM16A, squeezes out hidden conformational sites. At the same time, it verified the feasibility of protein transient conformation as a drug development target, providing new research ideas and inspirations for drug targets and original drug discovery.