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

Abstract

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 IKATP channels are pharmaceutical targets in type II diabetes or cardiac arrhythmia treatment. We have been suggested that IKATP inhibitors, glibenclamide and HMR1098, normalize CS channels. IKATP in response to Mg‐ATP, glibenclamide and HMR1098 were measured by inside‐out patch‐clamp electrophysiology. Results were interpreted in view of cryo‐EM IKATP 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.

Development of IKATP Ion Channel Blockers Targeting Sulfonylurea Resistant Mutant KIR6.2 Based Channels for Treating DEND Syndrome

“…Inside-out recordings presented here were performed in the absence of Mg-ATP and ADP in the bath solution, to best mimic the MD conditions. This most likely resulted in 6-11 fold higher glibenclamide IC 50 values than in the presence of 0.15 mM MgATP (Houtman et al, 2019), as seen also in measurements of tolbutamide block in presence and absence of ATP (Miyamura et al, 2000). Nevertheless, Q52R and L164P displayed reduced glibenclamide sensitivity as expected, which therefore is a MgATP independent characteristic.…”

“…23966) transfection was performed using either WT or mutant pCMV6-K IR 6.2 in combination with pCMV6-SUR2A and pEGFP1 (0.16, 0.16 and 0.08 μg, respectively). I KATP measurements were performed essentially as described before (Houtman et al, 2019). Briefly, glass capillary pipettes (Harvard Apparatus, cat.…”

Cantú syndrome: A new case and evolution of clinical conditions during first 2‐year follow‐up

“…So far, there are no target therapies for CS, and clinical management involves symptomatic treatments to address secondary complications. 1 Nevertheless, the K ATP channel is a known target for which both channel blocking and opening drugs are used in the clinic, 10 with numerous studies assessing the efficacy of this drugs underway. 10 , 14 , 15 At the moment, any conclusions on clinical efficacy awaits further studies.…”

“… 1 Nevertheless, the K ATP channel is a known target for which both channel blocking and opening drugs are used in the clinic, 10 with numerous studies assessing the efficacy of this drugs underway. 10 , 14 , 15 At the moment, any conclusions on clinical efficacy awaits further studies. 10 Remarkably, there is an overlapping phenotype (hypertrichosis, pericardial effusion, and edema) 16 in CS patients and people treated with minoxidil, a K ATP channel opener.…”

Computational Identification of Novel Kir6 Channel Inhibitors

“…Pipette resistance was 1.5–3 MΩ. Data were not corrected for rundown, which was less than 10% at 10 min as shown earlier (Houtman et al, 2019). All measurements were performed within a timeframe of 8–10 min.…”