Identification of a cluster of residues in transmembrane segment 6 of domain III of the cockroach sodium channel essential for the action of pyrethroid insecticides
Identification of a cluster of residues in transmembrane segment 6 of domain III of the cockroach sodium channel essential for the action of pyrethroid insecticides
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DOI：
10.1042/bj20082082
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发表时间：
2009-04-15
影响因子：
4.1
通讯作者：
Dong, Ke
中科院分区：
文献类型：
--
作者：
Du, Yuzhe;Lee, Jung-Eun;Dong, Ke
蟑螂BgNa(v)钠通道III结构域（IIIS6）第6跨膜段上的苯丙氨酸残基（Phe(1519)）是拟除虫菊酯结合和作用所必需的。然而，IIIS6中的其他残留物是否参与拟除虫菊酯类杀虫剂的作用仍有待确定。在本研究中，我们使用丙氨酸扫描诱变技术对BgNa(v)通道IIIS6中的20个残基进行了系统分析。我们的研究结果表明，四个残基IIe（1514）、Gly（1516）、Phe（1518）和Asn（1522）的丙氨酸取代改变了钠通道对拟除虫菊酯杀虫剂的敏感性。G1516A、F1518A和N1522A取代物降低了钠通道对所有七种拟除虫菊酯的敏感性，包括四种I型（在苯氧苯甲酰醇上缺乏-氰基）和三种II型（含有-氰基）拟除虫菊酯，而11514A取代物增强了钠通道对四种仅含有苯氧苯甲酰醇的I型和II型拟除虫菊酯的敏感性。我们还发现，亮氨酸（1521）和丝氨酸（1517）的丙氨酸/赖氨酸取代影响了BTX （batrachotoxin）的作用，但对拟除虫菊酯没有影响。在基于K(v)1.2的开放钠通道同源性模型中，Ile（1514）、Phe（1518）和Asn（1522）的侧链暴露于含有先前鉴定的拟除虫酯相互作用残基的螺旋IIS5和连接体IIS4-IIS5，而Ser（1517）和Leu（1521）则面向BTX受体所在的内孔。因此，本研究为结构模型提供了进一步的证据，其中拟除虫菊酯类化合物结合到由螺旋IIIS6， IIS5和连接螺旋IIS4-IIS5组成的脂质暴露界面，而BTX结合到IIIS6螺旋的孔暴露侧。
A phenylalanine residue (Phe(1519)) in the sixth transmembrane segment of domain III (IIIS6) of the cockroach BgNa(v) sodium channel is required for the binding and action of pyrethroids. However, whether or not other residues in IIIS6 participate in the action of pyrethroids remains to be determined. In the present study, we conducted a systematic analysis of 20 residues in IIIS6 of the BgNa(v) channel using alanine-scanning mutagenesis. Our results show that alanine substitutions of four residues, IIe(1514), Gly(1516), Phe(1518) and Asn(1522), altered sodium channel sensitivity to pyrethroid insecticides. Whereas the G1516A, F1518A and N1522A substitutions diminished sodium channel sensitivity to all seven pyrethroids examined, including four type I (lacking the alpha-cyano group at the phenoxybenzoyl alcohol) and three type II (containing the a-cyano group) pyrethroids, the 11514A substitution enhanced sodium channel sensitivity to four type I and type II pyrethroids that contain the phenoxybenzyl alcohol only. We also show that alanine/lysine substitutions of Leu(1521) and Ser(1517) affected the action of BTX (batrachotoxin), but not pyrethroids. In the K(v)1.2-based homology model of the open sodium channel, side chains of Ile(1514), Phe(1518) and Asn(1522) are exposed towards helix IIS5 and linker IIS4-IIS5, which contain previously identified pyrethroid-interacting residues, whereas Ser(1517) and Leu(1521) face the inner pore where the BTX receptor is located. Thus the present study provides further evidence for structural models in which pyrethroids bind to the lipid-exposed interface formed by helices IIIS6, IIS5 and linker helix IIS4-IIS5, whereas BTX binds to the pore-exposed side of the IIIS6 helix.