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Differential binding of tetrodotoxin and its derivatives to voltage‐sensitive sodium channel subtypes (Na v 1.1 to Na v 1.7)
Author(s) -
Tsukamoto Tadaaki,
Chiba Yukie,
Wakamori Minoru,
Yamada Tomoshi,
Tsunogae Shunsuke,
Cho Yuko,
Sakakibara Ryo,
Imazu Takuya,
Tokoro Shouta,
Satake Yoshiki,
Adachi Masaatsu,
Nishikawa Toshio,
YotsuYamashita Mari,
Konoki Keiichi
Publication year - 2017
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.13985
Subject(s) - tetrodotoxin , sodium channel , inhibitory postsynaptic potential , binding site , chemistry , stereochemistry , amino acid , hek 293 cells , sodium , microbiology and biotechnology , biophysics , biology , biochemistry , gene , neuroscience , organic chemistry
Background and Purpose The development of subtype‐selective ligands to inhibit voltage‐sensitive sodium channels (VSSCs) has been attempted with the aim of developing therapeutic compounds. Tetrodotoxin (TTX) is a toxin from pufferfish that strongly inhibits VSSCs. Many TTX analogues have been identified from marine and terrestrial sources, although their specificity for particular VSSC subtypes has not been investigated. Herein, we describe the binding of 11 TTX analogues to human VSSC subtypes Na v 1.1–Na v 1.7. Experimental Approach Each VSSC subtype was transiently expressed in HEK293T cells. The inhibitory effects of TTX analogues on each subtype were assessed using whole‐cell patch‐clamp recordings. Key Results The inhibitory effects of TTX on Na v 1.1–Na v 1.7 were observed in accordance with those reported in the literature; however, the 5‐deoxy‐10,7‐lactone‐type analogues and 4,9‐anhydro‐type analogues did not cause inhibition. Chiriquitoxin showed less binding to Na v 1.7 compared to the other TTX‐sensitive subtypes. Two amino acid residues in the TTX binding site of Na v 1.7, Thr 1425 and Ile 1426 were mutated to Met and Asp, respectively, because these residues were found at the same positions in other subtypes. The two mutants, Na v 1.7 T1425M and Na v 1.7 I1426D, had a 16‐fold and 5‐fold increase in binding affinity for chiriquitoxin, respectively. Conclusions and Implications The reduced binding of chiriquitoxin to Na v 1.7 was attributed to its C11–OH and/or C12–NH 2 , based on reported models for the TTX‐VSSC complex. Chiriquitoxin is a useful tool for probing the configuration of the TTX binding site until a crystal structure for the mammalian VSSC is solved.