Abstract
Aim:
KCNQ1 and KCNE1 form a complex in human ventricular cardiomyocytes, which are important in maintaining a normal heart rhythm. In the present study we investigated the effects of a homologous series of 1-alkanols on KCNQ1/KCNE1 channels expressed in Xenopus oocytes.
Methods:
ECG recording was made in rats injected with ethanol-containing solution (0.3 mL, ip). Human KCNQ1 channel and its auxiliary subunit KCNE1 were heterologously coexpressed in Xenopus oocytes, which were superfused with ND96 solution; 1-alkanols (ethanol, 1-butanol and 1-hexanol) were delivered through a gravity-driven perfusion device. The slow-delayed rectifier potassium currents IKs (KCNQ1/KCNE1 currents) were recorded using a two-electrode voltage clamp method. Site-directed mutations (I257A) were made in KCNQ1.
Results:
In ECG recordings, a low concentration of ethanol (3%, v/v) slightly increased the heart rate of rats, whereas the higher concentrations of ethanol (10%, 50%, v/v) markedly reduced it. In oocytes coexpressing KCNQ1/KCNE1 channels, ethanol, 1-butanol and 1-hexanol dose-dependently inhibited IKs currents with IC50 values of 80, 11 and 2.7 mmol/L, respectively. Furthermore, the 1-alkanols blocked the KCNQ1 channel in both open and closed states, and a four-state model could adequately explain the effects of 1-alkanols on the closed-state channel block. Moreover, the mutation of I257A at the intracellular loop between S4 and S5 in KCNQ1 greatly decreased the sensitivity to 1-alkanols; and the IC50 values of ethanol, 1-butanol and 1-hexanol were increased to 634, 414 and 7.4 mmol/L, respectively. The mutation also caused the ablation of closed-state channel block.
Conclusion:
These findings provide new insight into the intricate mechanisms of the blocking effects of ethanol on the KCNQ1 channel.
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Acknowledgements
We are grateful to Dr Bo ZHONG for the critical reading and our colleagues for their comments and discussions. This work was supported by the National Basic Research Program of China (No 2014CB910300), the National Natural Science Foundation of China grants (No 31271209 and 31328007), the Natural Science Foundation of Hubei Province (No 2015CFA095), and Specialized Research Fund for the Doctoral Program of Higher Education of Ministry of Education of China (No 20120142120062); Jing YAO was also supported by university fund (No 2042014KF0230).
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Xie, C., Liu, Hw., Pan, N. et al. The residue I257 at S4–S5 linker in KCNQ1 determines KCNQ1/KCNE1 channel sensitivity to 1-alkanols. Acta Pharmacol Sin 37, 124–133 (2016). https://doi.org/10.1038/aps.2015.133
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DOI: https://doi.org/10.1038/aps.2015.133
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