| Popis: |
Members of the TREK family of two-pore domain potassium channels are highly sensitive to regulation by membrane lipids, including phosphatidylinositol-4,5-bisphosphate (PIP2). Previous studies have demonstrated that PIP2increases TREK-1 channel activity; however, the mechanistic understanding of the conformational transitions induced by PIP2remain unclear. Here, we used coarse-grained molecular dynamics and atomistic molecular dynamics simulations to model the PIP2-binding site on both the up and down state conformations of TREK-1. We also calculated the free energy of PIP2binding relative to other anionic phospholipids in both conformational states using potential of mean force and free-energy-perturbation calculations. Our results identify state-dependent binding of PIP2to sites involving the proximal C-terminus, and we show that PIP2promotes a conformational transition from a down state toward an intermediate that resembles the up state. These results are consistent with functional data for PIP2regulation, and together provide evidence for a structural mechanism of TREK-1 channel activation by phosphoinositides. |
