Vais H, Williamson M S, Goodson S J, Devonshire A L, Warmke J W, Usherwood P N, Cohen C J
Division on Molecular Toxicology, School of Biology, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
J Gen Physiol. 2000 Mar;115(3):305-18. doi: 10.1085/jgp.115.3.305.
kdr and super-kdr are mutations in houseflies and other insects that confer 30- and 500-fold resistance to the pyrethroid deltamethrin. They correspond to single (L1014F) and double (L1014F+M918T) mutations in segment IIS6 and linker II(S4-S5) of Na channels. We expressed Drosophila para Na channels with and without these mutations and characterized their modification by deltamethrin. All wild-type channels can be modified by <10 nM deltamethrin, but high affinity binding requires channel opening: (a) modification is promoted more by trains of brief depolarizations than by a single long depolarization, (b) the voltage dependence of modification parallels that of channel opening, and (c) modification is promoted by toxin II from Anemonia sulcata, which slows inactivation. The mutations reduce channel opening by enhancing closed-state inactivation. In addition, these mutations reduce the affinity for open channels by 20- and 100-fold, respectively. Deltamethrin inhibits channel closing and the mutations reduce the time that channels remain open once drug has bound. The super-kdr mutations effectively reduce the number of deltamethrin binding sites per channel from two to one. Thus, the mutations reduce both the potency and efficacy of insecticide action.
kdr和超级kdr是家蝇及其他昆虫体内的突变，它们使昆虫对拟除虫菊酯溴氰菊酯产生30倍和500倍的抗性。它们分别对应于钠通道IIS6片段和连接子II（S4-S5）中的单个（L1014F）和双个（L1014F+M918T）突变。我们表达了带有和不带有这些突变的果蝇para钠通道，并对溴氰菊酯对其的修饰作用进行了表征。所有野生型通道都能被低于10 nM的溴氰菊酯修饰，但高亲和力结合需要通道开放：（a）短暂去极化脉冲序列比单次长时间去极化更能促进修饰；（b）修饰的电压依赖性与通道开放的电压依赖性相似；（c）来自沟迎风海葵的毒素II能促进修饰，它会减缓失活。这些突变通过增强关闭状态失活来减少通道开放。此外，这些突变分别使对开放通道的亲和力降低了20倍和100倍。溴氰菊酯抑制通道关闭，而这些突变减少了药物结合后通道保持开放的时间。超级kdr突变有效地将每个通道上溴氰菊酯结合位点的数量从两个减少到一个。因此，这些突变降低了杀虫剂作用的效力和效果。
