Interaction of batrachotoxin with the local anesthetic receptor site in transmembrane segment IVS6 of the voltage-gated sodium channel

被引:112
作者
Linford, NJ [1 ]
Cantrell, AR [1 ]
Qu, YS [1 ]
Scheuer, T [1 ]
Catterall, WA [1 ]
机构
[1] Univ Washington, Dept Pharmacol, Seattle, WA 98195 USA
关键词
D O I
10.1073/pnas.95.23.13947
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The voltage-gated sodium channel is the site of action of more than six classes of neurotoxins and drugs that alter its function by interaction with distinct, allosterically coupled receptor sites. Batrachotoxin (BTX) is a steroidal alkaloid that binds to neurotoxin receptor site 2 and causes persistent activation. BTX binding is inhibited allosterically by local anesthetics, We have investigated the interaction of BTX with amino acid residues I1760, F1764, and Y1771, which form part of local anesthetic receptor site in transmembrane segment IVS6 of type IIA sodium channels. Alanine substitution for F1761 (mutant F1764A) reduces tritiated BTX-A-20-alpha-benzoate binding affinity, causing a 60-fold increase in K-d. Alanine substitution for I1760, which is adjacent to F1764 in the predicted 1VS6 transmembrane alpha helix, causes only a 4-fold increase in Kd In contrast, mutant Y1771A shows no change in BTX binding affinity. For wildtype and mutant Y1771A, BTX shifted the voltage for half-maximal activation approximate to 40 mV in the hyperpolarizing direction and increased the percentage of noninactivating sodium current to approximate to 60%. In contrast, these BTX effects mere eliminated completely for the F1764A mutant and were reduced substantially for mutant I1760A. Our data suggest that the BTX receptor site shares overlapping but nonidentical molecular determinants with the local anesthetic receptor site in transmembrane segment 1VS6 as well as having unique molecular determinants in transmembrane segment IS6, as demonstrated in previous work. Evidently, BTX conforms to a domain-interface allosteric model of ligand binding and action, as previously proposed for calcium agonist and antagonist drugs acting on L-type calcium channels.
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页码:13947 / 13952
页数:6
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