Block Effect Of Capsaicin On The Human HERG Potassium Currents Was Enhanced By S6 Mutation At Y652

Aim: The objectives of this study were to investigate the inhibitory action of capsaicin on wild-type and mutation HERG K+ channel current(IHERG), and to determine whether mutations in the S6 region are significant for the inhibition of IHERG by capsaicin.Methods: HERG channels (WT, Y652A and F656A) were expressed in Xenopus oocytes and studied using standard two-microelectrode voltage-clamp techniques.Results: Capsaicin blocks WT HERG in a concentration-dependent manner, with an IC50 of 17.45μM and a negative shift in the steady state inactivation curve. Our data are 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 5.68μM, whereas mutation of F656A doesn't significantly alter drug potency. Simultaneously, for Y652A,the steady state activation parameter is shifted to more positive value by 5mV and the inactivation parameter is shifted to more negative value by -29mV in the presence of 25μM capsaicin.Conclusion: Capsaicin blocks HERG channels by binding to both the closed and open channel states .Y652 is one of the critical residues in the capsaicin-binding sites. Mutation of Y652A enhancing the drug block,which probably cause some patients particularly sensitive to capsaicin in clinic.