Glibenclamide and HMR1098 normalize Cantú syndrome‐associated gain‐of‐function currents

Cantú syndrome (CS) is caused by dominant gain‐of‐function mutation in ATP‐dependent potassium channels. Cellular ATP concentrations regulate potassium current thereby coupling energy status with membrane excitability. No specific pharmacotherapeutic options are available to treat CS but I_KATP channels are pharmaceutical targets in type II diabetes or cardiac arrhythmia treatment. We have been suggested that I_KATP inhibitors, glibenclamide and HMR1098, normalize CS channels. I_KATP in response to Mg‐ATP, glibenclamide and HMR1098 were measured by inside‐out patch‐clamp electrophysiology. Results were interpreted in view of cryo‐EM I_KATP channel structures. Mg‐ATP IC₅₀ values of outward current were increased for D207E (0.71 ± 0.14 mmol/L), S1020P (1.83 ± 0.10), S1054Y (0.95 ± 0.06) and R1154Q (0.75 ± 0.13) channels compared to H60Y (0.14 ± 0.01) and wild‐type (0.15 ± 0.01). HMR1098 dose‐dependently inhibited S1020P and S1054Y channels in the presence of 0.15 mmol/L Mg‐ATP, reaching, at 30 μmol/L, current levels displayed by wild‐type and H60Y channels in the presence of 0.15 mmol/L Mg‐ATP. Glibenclamide (10 μmol/L) induced similar normalization. S1054Y sensitivity to glibenclamide increases strongly at 0.5 mmol/L Mg‐ATP compared to 0.15 mmol/L, in contrast to D207E and S1020P channels. Experimental findings agree with structural considerations. We conclude that CS channel activity can be normalized by existing drugs; however, complete normalization can be achieved at supraclinical concentrations only.