Voltage-gated sodium channels (Nav) are essential for electrical signaling in the nervous system. They are also the primary targets of several classes of insecticides including pyrethroids. There is only one sodium channel gene in most insect species, whereas mammals possess at least nine sodium channel genes. Extensive alternative splicing and RNA editing of sodium channel transcripts have been documented in many insect species. However, the functional consequences of these post-transcriptional events have been evaluated only in DmNav and BgNav from Drosophila melanogaster and Blattella germanica, respectively. In this study, we isolated 41 full-length cDNA clones encoding 34 sodium channel (NlNav) variants from a major rice pest, the brown planthopper (Nilaparvata lugens Stål). The 34 NlNav variants represent 24 distinct splicing types based on the usage of nine alternative exons, six of which, including exon b, have been previously reported in other insect species. When expressed in Xenopus oocytes, NlNav variants lacking exon b generated significantly larger sodium currents than variants possessing exon b, suggesting an inhibitory effect of exon b on sodium current expression. A similar effect has been reported for exon b from BgNav. Mutational analysis showed that three conserved amino acid residues encoded by exon b are critical for its inhibitory effect. In addition, mutually exclusive exons k/l contribute to distinct functional properties and channel sensitivity to pyrethroids. Altogether, these results show that alternative splicing generates functional diversity of sodium channels in this insect species and that the role of exon b in regulating neuronal excitability is likely conserved among insect species.

中文翻译：

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钠通道变体的不同功能特性与Nilaparvata lugens中其他外显子的使用有关。

电压门控钠通道（Nav）对于神经系统中的电信号传递至关重要。它们也是包括拟除虫菊酯在内的几种杀虫剂的主要目标。在大多数昆虫物种中，只有一个钠通道基因，而哺乳动物至少具有九个钠通道基因。钠通道转录物的广泛的选择性剪接和RNA编辑已在许多昆虫物种中得到记录。但是，这些转录后事件的功能后果仅在果蝇和德国小Bl的DmNav和BgNav中进行了评估。在这项研究中，我们从一个主要的水稻害虫棕色飞虱（Nilaparvata lugensStål）中分离了41个全长cDNA克隆，编码34个钠通道（NlNav）变体。基于九个替代外显子的使用，这34个NlNav变体代表24种不同的剪接类型，其中六个（包括外显子b）已在其他昆虫物种中进行了报道。当在非洲爪蟾卵母细胞中表达时，缺少外显子b的NlNav变异体比拥有外显子b的变异体产生更大的钠电流，这表明外显子b对钠电流表达具有抑制作用。已经报道了来自BgNav的外显子b的类似作用。突变分析表明，外显子b编码的三个保守氨基酸残基对其抑制作用至关重要。另外，互斥的外显子k / l有助于不同的功能特性和对拟除虫菊酯的通道敏感性。共，