PIP2 tunes voltage sensor-targeted drug modulation of Kv7.2

KCNQ/Kv7 channels exhibit remarkable responses to diverse small molecule modulators, and this is a potential therapeutic avenue for several neurological conditions characterized by hyperexcitability. One class of Kv7 positive modulators, including the benzamide ICA-069673, targets a pocket formed by residues in the voltage-sensing domain (VSD). In this study, we explored the effects of PIP2 levels on the efficacy and subunit stoichiometry of ICA-069673 responses in Kv7.2, using concatenated Kv7.2 constructs to control the ratio of drug-sensitive and insensitive subunits in individual channels. In ambient PIP2, a full complement of four drug-sensitive subunits is required for full efficacy of ICA-069673, manifested as a pronounced hyperpolarizing shift of voltage-dependence of activation, delayed deactivation, and augmentation of current amplitude. By overexpressing a PI(4)P 5-kinase enzyme to increase PIP2 levels, we observed that elevated PIP2 strongly rescued ICA-069673 responses in concatemers containing up to 3 drug-insensitive subunits. Furthermore, increased PIP2 markedly enhanced the effects of ICA-069673 and another VSD-targeted drug, QO-58, on Kv7.2 deactivation. In summary, these results reveal a fundamental role of PIP2 in pharmacological modulation of Kv7.2 by VSD-targeted drugs.