Novel Kv7.1-Phosphatidylinositol 4,5-Bisphosphate Interaction Sites Uncovered by Charge Neutralization Scanning

Competition of calcified calmodulin N lobe and PIP2to an LQT mutation site in Kv7.1 channel

“…(ii) K526 and K527 had a substantial impact on PIP 2 binding, even in the context of other potential PIP 2 binding sites (Fig. 6) (32,(37)(38)(39). (iii) In contrast to WT CaM, the CaM mutant K75N was unable to compete with PIP 2 binding to Kv7.1 CT in the presence of Ca 2+ and rescue the current rundown arising from PIP 2 depletion, suggesting that it does not properly interact with Kv7.1 helix B (Fig.…”

“…After receptor-mediated PIP 2 depletion and increased cytosolic Ca 2+ , we suggest that the calcified CaM C lobe unbinds helix A and that the calcified CaM N lobe displaces PIP 2 from its binding site in helix B to limit the decrease in I KS channel activity arising from PIP 2 hydrolysis. helix B, several PIP 2 molecules bind to Kv7.1 channels at multiple contact sites or migrate to different places, including those located at the S2-S3 and S4-S5 intracellular linkers, prehelix A, and helix C, to achieve a specific function (33,37,38 (Fig. 2). (ii) PIP 2 lowers the binding affinity of Kv7.1 proximal CT for CaM in the presence of Ca 2+ but does not in its absence as measured by D-CaM fluorescence (Fig.…”

“…Recent studies identified clusters of basic residues in the Kv7.1 membrane domain, specifically at the S2-S3 and S4-S5 intracellular linkers and in prehelix A, to be involved in PIP 2 binding (33,37,38). Another cluster of basic residues in helix C was also found to be involved in Kv7.1 current rundown after PIP 2 depletion (32,39).…”

“…Several clusters of basic residues have been identified in the Kv7.1 CT as potential PIP 2 binding sites, including sites in prehelix A and helix C (32,34,37,39). Therefore, we purified Histagged Kv7.1 CT that lacks helices C and D (352-539, Δ406-504) and checked whether the competition of Ca 2+ -CaM to PIP 2 binding still occurred in PIP 2 pulldown assays.…”

Modulation of Kv7 channels and excitability in the brain

“…PIP 2 is a co-factor for numerous ion channels and transporters [29], including Kv7, that alters channel function and often is obligatory for activation [30–33]. While it has been known that PIP 2 interaction with Kv7 is mandatory for channel function [34,35], more recently it was shown that PIP 2 has multiple sites of interaction within the channel, with varying effects [36]. One such PIP 2 interaction modulates coupling the voltage-sensing to the pore-gating domain [37–40].…”