Calcium-activated chloride channel TMEM16A opens via pi-helical transition in transmembrane segment 4

• 成果类型: Article
• 署名作者: Kostritskii, Andrei Y.; Kostritskaia, Yulia; Dmitrieva, Natalia; Stauber, Tobias; Machtens, Jan-Philipp
• 署名单位: Helmholtz Association; Research Center Julich; MSH Medical School Hamburg; Hannover Medical School
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11032
• DOI: 10.1073/pnas.2421900122
• 发表日期: 2025-05-06
• 关键词: particle mesh ewald; molecular-dynamics; phosphatidylinositol 4; 5-bisphosphate; independent activation; protein; sensitivity; database; currents; pores; field

摘要

TMEM16A is a Ca2+-activated Cl-channel that has crucial roles in various physiological and pathological processes. However, the structure of the open state of the channel and the mechanism of Ca2+-induced pore opening have remained elusive. Using extensive molecular dynamics simulations, protein structure prediction, and patch-clamp electrophysiology, we demonstrate that TMEM16A opens a hydrated Cl--conductive pore via a pi-helical transition in transmembrane segment 4 (TM4). We also describe a coupling mechanism that links pi-helical transition and pore opening to the Ca2+-induced conformational changes in TMEM16A. Furthermore, we designed a pi-helix-stabilizing mutation (I551P) that facilitates TMEM16A activation, revealing atomistic details of the ion-conduction mechanism. Finally, AlphaFold2 structure predictions revealed the importance of the pi helix in TM4 to structure-function relations in TMEM16 and the related OSCA/TMEM63 family, further highlighting the relevance of dynamic pi helices for gating in various ion channels.