Abstract
Inwardly rectifying potassium (Kir) channels play key roles in regulating membrane potential and potassium transport through voltage-dependent inhibition by cytoplasmic Mg²⁺ and polyamines. Despite decades of extensive studies, the structural basis for polyamine-mediated inward rectification remains unclear. Here, we present cryo-EM structures of the heteromeric Kir4.1/5.1 channel—which is critical for brain and kidney function and whose dysfunction causes EAST/SeSAME syndrome—in its apo state and in complex with spermine, a channel blocker named VU0134992, and EHop-016, an inhibitor identified in this study. The structures of Kir4.1/5.1, in an opposite 2:2 heterotetrameric assembly, suggest an inner-ring blockage mechanism, where polyamines and channel blockers with different stoichiometries bind in a membrane-parallel orientation at the upper site of the transmembrane central cavity. Together with electrophysiology and molecular dynamics simulations, our findings provide mechanistic insights into inward rectification, channel inhibition, and the pharmacology of Kir channels.
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Acknowledgments
We thank the Cryo-Electron Microscopy Center at the Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, and the ShanghaiTech Cryo-EM Imaging Facility for their assistance with data collection.
Funding
This work was supported by the National Natural Science Foundation of China grant (grant no. 32471016 to J.G. and T2321001 to C.S.), Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB0830403 to Z.G.), the Shanghai Lingang Laboratory (grant no. LG-QS-202203-03 to J.Y. and LG-QS-202203-05 to J.G.), Shanghai Pujiang Program (to J.G.) and Shanghai Basic Research Pioneer Project (to J.Y.), China National Postdoctoral Program for Innovative Talents (grant no. BX20240397 to X.Z.), National Natural Science Foundation of China (grant no. 82404594 to X.Z.), China Postdoctoral Science Foundation (grant no. 2024M753376 to X.Z.) and Sanofi Scholarship Program (to X.Z.).
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Ning, Y., Zhou, X., Zhang, Y. et al. Cryo-EM structures of heteromeric Kir4.1/5.1 channel suggest mechanisms of inward rectification and channel blockage. Nat Commun (2026). https://doi.org/10.1038/s41467-026-74087-9
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DOI: https://doi.org/10.1038/s41467-026-74087-9
