The Potential Molecular Mechanism Of The Blockade Effect Of Neochamaejasmin A On K_V1.4 Channels

Stellera chamaejasme L.(Thymelaeaceae)is a toxic perennial herb that is widespread in Mongolia,Tibet and the northern parts of China.Neochamaejasmin A(NCA),one of main active ingredients in the root of Stellera chamaejasme L.,has a variety of pharmacological effects.However,whether there are any functions on ion channels is unknown.K_V1.4 channel belongs to the voltage-gated K+ channel family,mainly distributed in the brain,myocardium and skeletal muscle of humans and mammals,with important physiological functions.Method: In this study,we used whole cell patch clamp technique to investigate whether NCA works on Kv1.4 and alanine scanning to find its potential binding sites.Results:1.The IC50 of NCA on K_V1.4 channels is 7.55 ?M.2.The V560 A and V549 A mutants in pore domain can significantly alleviate the NCA blocking effects,suggesting that they are the important binding sites of NCA.3.However,data suggested that there are no use-dependence phenomenons of the blockage.NCA had no effect on the channel steady state activation,inactivation and recovery of inactivation.4.Since site of K531 has suggested in many drug binding studies,we also tested this site.However,K531 A mutants show no significant effects over the blockage.Conclusion: the IC50 of NCA on K_V1.4 channels is 7.55 ?M,the sites V560 and V549 on k_v1.4 are the potential binding sites of NCA.