Voltage-gated sodium channels (VGSCs) are a major target site for the action of pyrethroid insecticides and resistance to pyrethroids has been ascribed to mutations in the VGSC gene. VGSCs in insects are encoded by only one gene and their structural and functional diversity results from posttranscriptional modification, particularly, alternative splicing. Using whole cell patch clamping of neurons from pyrethroid susceptible (wild-type) and resistant strains (s-kdr) of housefly, Musca domestica, we have shown that the V50 for activation and steady state inactivation of sodium currents (INa+) is significantly depolarised in s-kdr neurons compared with wild-type and that 10 nM deltamethrin significantly hyperpolarised both of these parameters in the neurons from susceptible but not s-kdr houseflies. Similarly, tail currents were more sensitive to deltamethrin in wild-type neurons (EC15 14.5 nM) than s-kdr (EC15 133 nM). We also found that in both strains, INa+ are of two types: a strongly inactivating (to 6.8% of peak) current, and a more persistent (to 17.1% of peak) current. Analysis of tail currents showed that the persistent current in both strains (wild-type EC15 5.84 nM) was more sensitive to deltamethrin than was the inactivating type (wild-type EC15 35.1 nM). It has been shown previously, that the presence of exon l in the Drosophila melanogaster VGSC gives rise to a more persistent INa+ than does the alternative splice variant containing exon k and we used PCR with housefly head cDNA to confirm the presence of the housefly orthologues of splice variants k and l. Their effect on deltamethrin sensitivity was determined by examining INa+ in Xenopus oocytes expressing either the k or l variants of the Drosophila para VGSC. Analysis of tail currents, in the presence of various concentrations of deltamethrin, showed that the l splice variant was significantly more sensitive (EC50 42 nM) than the k splice variant (EC50 866 nM). We conclude that in addition to the presence of point mutations, target site resistance to pyrethroids may involve the differential expression of splice variants.

中文翻译：

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敲除抗性突变和选择性剪接对家蝇和果蝇果蝇的电压门控钠通道的影响。

电压门控钠通道（VGSC）是拟除虫菊酯类杀虫剂作用的主要目标部位，并且对拟除虫菊酯类药物的抗药性归因于VGSC基因的突变。昆虫中的VGSC仅由一个基因编码，其结构和功能多样性是由转录后修饰（特别是选择性剪接）产生的。使用全细胞膜片钳住拟除虫菊酯易感（野生型）和抗性菌株（s-kdr）家蝇（Musca domestica）的神经元，我们已经表明，用于激活和稳定钠电流（INa +）的V50明显去极化了与野生型相比，s-kdr神经元中的10％溴氰菊酯显着超极化了来自易感但不是s-kdr家蝇的神经元中的这两个参数。同样，尾电流对野生型神经元中的溴氰菊酯（EC15 14.5 nM）比s-kdr（EC15 133 nM）更敏感。我们还发现，在两种菌株中，INa +都有两种类型：强烈失活（至峰值的6.8％）电流和更持久的（至峰值的17.1％）电流。尾电流分析表明，两种菌株（野生型EC15 5.84 nM）中的持续电流比灭活型（野生型EC15 35.1 nM）对溴氰菊酯更敏感。先前已证明，果蝇VGSC中外显子1的存在比包含外显子k的替代剪接变体产生更持久的INa +，我们将PCR与家蝇头部cDNA一起使用以确认存在的家蝇直向同源物剪接变体k和l。通过检查表达果蝇对VGSC的k或l变体的爪蟾卵母细胞中的INa +，确定它们对溴氰菊酯敏感性的影响。在存在各种浓度的溴氰菊酯的情况下对尾电流的分析表明，l剪接变体（EC50为42 nM）比k剪接变体（EC50 866 nM）要敏感得多。我们得出的结论是，除存在点突变外，对拟除虫菊酯的靶位点抗性可能涉及剪接变体的差异表达。