Structural determinants of ivabradine block of the open pore of HCN4

• 成果类型: Article
• 署名作者: Saponaro, Andrea; Krumbach, Jan H.; Chaves-Sanjuan, Antonio; Sharifzadeh, Atiyeh Sadat; Porro, Alessandro; Castelli, Roberta; Hamacher, Kay; Bolognesi, Martino; DiFrancesco, Dario; Clarke, Oliver B.; Thiel, Gerhard; Moroni, Anna
• 署名单位: University of Milan; Technical University of Darmstadt; Technical University of Darmstadt; Technical University of Darmstadt; University of Milan; Consiglio Nazionale delle Ricerche (CNR); Columbia University; Columbia University; NewYork-Presbyterian Hospital; Columbia University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11362
• DOI: 10.1073/pnas.2402259121
• 发表日期: 2024-07-02
• 关键词: pacemaker channels; funny current; current i(f); sinoatrial; rabbit; activation; insights; binding

摘要

HCN1- 4 channels are the molecular determinants of the If/Ih current that crucially regulates cardiac and neuronal cell excitability. HCN dysfunctions lead to sinoatrial block (HCN4), epilepsy (HCN1), and chronic pain (HCN2), widespread medical conditions awaiting subtype- specific treatments. Here, we address the problem by solving the cryo- EM structure of HCN4 in complex with ivabradine, to date the only HCN- specific drug on the market. Our data show ivabradine bound inside the open pore at 3 angstrom resolution. The structure unambiguously proves that Y507 and I511 on S6 are the molecular determinants of ivabradine binding to the inner cavity, while F510, pointing outside the pore, indirectly contributes to the block by controlling Y507. Cysteine 479, unique to the HCN selectivity filter (SF), accelerates the kinetics of block. Molecular dynamics simulations further reveal that ivabradine blocks the permeating ion inside the SF by electrostatic repulsion, a mechanism previously proposed for quaternary ammonium ions.