The dynamic interplay of PIP₂ and ATP in the regulation of the K_ATP channel

ATP-sensitive potassium (K_ATP ) channels couple the intracellular ATP concentration to insulin secretion. K_ATP channel activity is inhibited by ATP binding to the Kir6.2 tetramer and activated by phosphatidylinositol 4,5-bisphosphate (PIP₂ ). Here, we use molecular dynamics simulation, electrophysiology and fluorescence spectroscopy to show that ATP and PIP₂ occupy different binding pockets that share a single amino acid residue, K39. When both ligands are present, simulations suggest that K39 shows a greater preference to co-ordinate with PIP₂ than with ATP. They also predict that a neonatal diabetes mutation at K39 (K39R) increases the number of hydrogen bonds formed between K39 and PIP₂ , potentially accounting for the reduced ATP inhibition observed in electrophysiological experiments. Our work suggests that PIP₂ and ATP interact allosterically to regulate K_ATP channel activity. KEY POINTS: The K_ATP channel is activated by the binding of phosphatidylinositol 4,5-bisphosphate (PIP₂ ) lipids and inactivated by the binding of ATP. K39 has the potential to bind to both PIP₂ and ATP. A mutation to this residue (K39R) results in neonatal diabetes. This study uses patch-clamp fluorometry, electrophysiology and molecular dynamics simulation. We show that PIP₂ competes with ATP for K39, and this reduces channel inhibition by ATP. We show that K39R increases channel affinity to PIP₂ by increasing the number of hydrogen bonds with PIP₂ , when compared with the wild-type K39. This therefore decreases K_ATP channel inhibition by ATP.