The second PI(3,5)P2 binding site in the S0 helix of KCNQ1 stabilizes PIP2-at the primary PI1 site with potential consequences on intermediate-to-open state transition

Biol Chem. 2023 Feb 23;404(4):241-254. doi: 10.1515/hsz-2022-0247. Print 2023 Mar 28.

Abstract

The Phosphatidylinositol 3-phosphate 5-kinase Type III PIKfyve is the main source for selectively generated phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), a known regulator of membrane protein trafficking. PI(3,5)P2 facilitates the cardiac KCNQ1/KCNE1 channel plasma membrane abundance and therewith increases the macroscopic current amplitude. Functional-physical interaction of PI(3,5)P2 with membrane proteins and its structural impact is not sufficiently understood. This study aimed to identify molecular interaction sites and stimulatory mechanisms of the KCNQ1/KCNE1 channel via the PIKfyve-PI(3,5)P2 axis. Mutational scanning at the intracellular membrane leaflet and nuclear magnetic resonance (NMR) spectroscopy identified two PI(3,5)P2 binding sites, the known PIP2 site PS1 and the newly identified N-terminal α-helix S0 as relevant for functional PIKfyve effects. Cd2+ coordination to engineered cysteines and molecular modeling suggest that repositioning of S0 stabilizes the channel s open state, an effect strictly dependent on parallel binding of PI(3,5)P2 to both sites.

Keywords: electrophysiology; molecular modeling; phosphatidylinositol; phosphoinositides; phospholipid; potassium channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Cell Membrane / metabolism
  • KCNQ1 Potassium Channel* / chemistry
  • KCNQ1 Potassium Channel* / genetics
  • KCNQ1 Potassium Channel* / metabolism
  • Mutation
  • Phosphatidylinositol 4,5-Diphosphate* / chemistry
  • Phosphatidylinositol 4,5-Diphosphate* / metabolism

Substances

  • Phosphatidylinositol 4,5-Diphosphate
  • KCNQ1 Potassium Channel