[Inhibition of Jingzhaotoxin-V on Kv4.3 channel].
Kv4.3 channel is present in many mammalian tissues, predominantly in the heart and central nervous system. Its currents are transient, characterized by rapid activation and inactivation. In the hearts of most mammals, it is responsible for repolarization of the action potential of ventricular myocytes and is important in the regulation of the heart rate. Because of its central role in this important physiological process, Kv4.3 channel is a promising target for anti-arrhythmic drug development. Jingzhaotoxin-V (JZTX-V) is a novel peptide neurotoxin isolated from the venom of the spider Chilobrachys jingzhao. Whole-cell patch clamp recording showed that it partly blocked the transient outward potassium channels in dorsal root ganglion neurons of adult rats with an IC(50) value of 52.3 nmol/L. To investigate the effect of JZTX-V on Kv4.3 channel, JZTX-V was synthesized using the solid-phase chemical synthesis and separated by reverse phase high performance liquid chromatography (HPLC). The purity was tested by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MOLDI-TOF mass spectrometry). Two-electrode voltage-clamp technique was used to characterize the action of JZTX-V on Kv4.3 channels expressed in Xenopus laevis oocytes. As a result, JZTX-V displayed fast kinetics of inhibition and recovery from inactivation. Furthermore, it could inhibit Kv4.3 channel current in a time- and concentration-dependent manner with an IC(50) value of 425.1 nmol/L. The application of JZTX-V affected the activation and inactivation characteristics of Kv4.3 channel and caused a shift of the current-voltage relationship curve and the steady-state inactivation curve to depolarizing direction by approximately 29 mV and 10 mV, respectively. So we deduced that JZTX-V is a gating modifier toxin of Kv4.3 channel. Present findings should be helpful to develop JZTX-V into a molecular probe and drug candidate targeting to Kv4.3 channel in the myocardium.
Cai
Li-Jun
LJ
Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, Hunan Normal University, Changsha, China.
Xu
De-Hong
DH
Luo
Ji
J
Chen
Ren-Zhong
RZ
Chi
Yu-Peng
YP
Zeng
Xiong-Zhi
XZ
Wang
Xian-Chun
XC
Liang
Song-Ping
SP
D000818:Animals; D005727:Ganglia, Spinal / Q000166:cytology*; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000494:pharmacology*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D051672:Shal Potassium Channels / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology*; D014982:Xenopus laevis
D009498:Neurotoxins; D010455:Peptides; D026902:Potassium Channel Blockers; D051672:Shal Potassium Channels; D013111:Spider Venoms