Block effect of capsaicin on hERG potassium currents is enhanced by S6 mutation at Y652

The objectives of this study were to investigate the inhibitory action of capsaicin on wild-type (WT) and mutation human ether-a-go-go-related gene (hERG) potassium channel currents (IhERG), and to determine whether mutations in the S6 region are significant for the inhibition of IhERG by capsaicin. The hERG channel (WT, Y652A and F656A) was expressed in Xenopus oocytes and studied using standard two-microelectrode voltage-clamp techniques. The results show that capsaicin blocks WT hERG in a concentration-dependent manner, with an IC50 of 17.45 μM and a negative shift in the steady-state inactivation curve. Characteristics of blockade were consistent with capsaicin causing components of block in both the closed and open channel states. However, mutating the Y652 residue to Ala enhances the blockade effect of capsaicin with an IC50 of 4.11 μM, whereas mutation of F656A does not significantly alter drug potency. Simultaneously, for Y652A, the steady-state activation parameter is shifted to a more positive value by 5 mV and the inactivation parameter is shifted to a more negative value by − 29 mV in the presence of 25 μM capsaicin. In conclusion, capsaicin blocks hERG channels by binding to both the closed and open channel states.Y652 was important as a molecular determinant of blockade. Mutation Y652A enhances the drug block, which may cause some patients to be particularly sensitive to capsaicin clinically.