title: Molecular basis of the inhibition of the fast inactivation of voltage-gated sodium channel Nav1.5 by tarantula toxin Jingzhaotoxin-II.
abstract: Jingzhaotoxin-II (JZTX-II) is a 32-residue peptide from the Chinese tarantula Chilobrachys jingzhao venom, and preferentially inhibits the fast inactivation of the voltage-gated sodium channels (VGSCs) in rat cardiac myocytes. In the present study, we elucidated the action mechanism of JZTX-II inhibiting hNav1.5, a VGSC subtype mainly distributed in human cardiac myocytes. Among the four VGSC subtypes tested, hNav1.5 was the most sensitive to JZTX-II (EC50=125±4nM). Although JZTX-II had little or no effect on steady-state inactivation of the residual currents conducted by hNav1.5, it caused a 10mV hyperpolarized shift of activation. Moreover, JZTX-II increased the recovery rate of hNav1.5 channels, which should lead to a shorter transition from the inactivation to closed state. JZTX-II dissociated from toxin-channel complex via extreme depolarization and subsequently rebound to the channel upon repolarization. Mutagenesis analyses showed that the domain IV (DIV) voltage-sensor domain (VSD) was critical for JZTX-II binding to hNav1.5 and some mutations located in S1-S2 and S3-S4 extracellular loops of hNav1.5 DIV additively reduced the toxin sensitivity of hNav1.5. Our data identified the mechanism underlying JZTX-II inhibiting hNav1.5, similar to scorpion α-toxins, involving binding to neurotoxin receptor site 3.
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhou
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Tang
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
authors.forename: Yunxiao
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha 410208, Hunan, China.
authors.forename: Huai
authors.initials: H
authors.lastname: Tao
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, China. Electronic address: liuzh@hunnu.edu.cn.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000737:chemistry* / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D051381:Rats; D026941:Sodium Channel Blockers / Q000737:chemistry* / Q000494:pharmacology; D013111:Spider Venoms / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D062554:NAV1.5 Voltage-Gated Sodium Channel; C568322:Scn5a protein, rat; D026941:Sodium Channel Blockers; D013111:Spider Venoms; C533889:jingzhaotoxin-II, Chilobrachys jingzhao
keywords: Action mechanism; Jingzhaotoxin-II; Nav1.5