Dynamic PIP₂ interactions with voltage sensor elements contribute to KCNQ2 channel gating

The S4 segment and the S4-S5 linker of voltage-gated potassium (Kv) channels are crucial for voltage sensing. Previous studies on the Shaker and Kv1.2 channels have shown that phosphatidylinositol-4,5-bisphosphate (PIP ₂) exerts opposing effects on Kv channels, upregulating the current amplitude, while decreasing the voltage sensitivity. Interactions between PIP₂ and the S4 segment or the S4-S5 linker in the closed state have been highlighted to explain the effects of PIP₂ on voltage sensitivity. Here, we show that PIP₂ preferentially interacts with the S4-S5 linker in the open-state KCNQ2 (Kv7.2) channel, whereas it contacts the S2-S3 loop in the closed state. These interactions are different from the PIP₂-Shaker and PIP₂-Kv1.2 interactions. Consistently, PIP₂ exerts different effects on KCNQ2 relative to the Shaker and Kv1.2 channels; PIP₂ up-regulates both the current amplitude and voltage sensitivity of the KCNQ2 channel. Disruption of the interaction of PIP₂ with the S4-S5 linker by a single mutation decreases the voltage sensitivity and current amplitude, whereas disruption of the interaction with the S2-S3 loop does not alter voltage sensitivity. These results provide insight into the mechanism of PIP₂ action on KCNQ channels. In the closed state, PIP₂ is anchored at the S2-S3 loop; upon channel activation, PIP₂ interacts with the S4-S5 linker and is involved in channel gating.