GPCR 中的天然变异和工程突变促进了秀丽隐杆线虫的避蚊胺抗性,Nature

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GPCR 中的天然变异和工程突变促进了秀丽隐杆线虫的避蚊胺抗性
Nature ( IF 50.5 ) Pub Date : 2018-09-26 , DOI: 10.1038/s41586-018-0546-8
Emily J Dennis ₁ , May Dobosiewicz ₂ , Xin Jin _{2,

3} , Laura B Duvall ₁ , Philip S Hartman ₄ , Cornelia I Bargmann _{2,

5} , Leslie B Vosshall _{1,

5,

6}

Affiliation

避蚊胺（N,N-二乙基-间甲苯甲酰胺）是美国农业部于 1946 年在筛选驱虫剂中发现的一种合成化学品，可保护士兵免受蚊媒疾病的侵害1,2。自发现以来，避蚊胺已成为世界上使用最广泛的节肢动物驱虫剂，对经过数百万年进化分离的无脊椎动物有效，包括咬蝇 3、蜜蜂 4、蜱 5 和陆蛭 3。在昆虫中，避蚊胺作用于嗅觉系统 5-12 并需要嗅觉受体共同受体 Orco7,9-12，但它究竟是如何工作的仍然存在争议13。在这里，我们表明线虫秀丽隐杆线虫对避蚊胺很敏感，并使用这种遗传易处理的动物来研究这种化学物质的作用机制。我们发现避蚊胺不是挥发性驱虫剂，而是选择性地干扰对各种引诱剂和驱避剂分子的趋化性。在对避蚊胺抗性蠕虫的正向遗传筛选中，我们确定了一个基因，该基因编码单个 G 蛋白偶联受体 str-217，该受体在一对对避蚊胺有反应的化学感应神经元中表达，称为 ADL 神经元。str-217 在另一个化学感应神经元中的错误表达赋予了对避蚊胺的反应。工程化的 str-217 突变体和携带 str-217 缺失的线虫野生分离物对避蚊胺具有抗性。我们发现避蚊胺可以通过增加运动过程中的平均停顿长度来干扰行为，并表明这种停顿的增加需要 str-217 和 ADL 神经元。最后，我们证明了 ADL 神经元被避蚊胺激活，并且 ADL 神经元的光遗传学激活增加了平均停顿长度。这与“混淆”假说一致，该假说认为避蚊胺不是一种简单的驱虫剂，而是调节多种嗅觉通路来扰乱行为反应 10,11。我们的结果表明避蚊胺在广泛不同的分类群中的有效性具有一致的主题：对多个化学感应神经元的影响，破坏气味刺激和行为反应之间的配对。避蚊胺选择性干扰秀丽隐杆线虫线虫的趋化性和 str-217 突变基因或表达它的一对化学感应神经元的沉默使蠕虫对避蚊胺具有抗性。这表明避蚊胺不是一种简单的驱虫剂，而是调节多种嗅觉途径来扰乱行为反应10,11。我们的结果表明避蚊胺在广泛不同的分类群中的有效性具有一致的主题：对多个化学感应神经元的影响，破坏气味刺激和行为反应之间的配对。避蚊胺选择性干扰秀丽隐杆线虫线虫的趋化性和 str-217 突变基因或表达它的一对化学感应神经元的沉默使蠕虫对避蚊胺具有抗性。这表明避蚊胺不是一种简单的驱虫剂，而是调节多种嗅觉途径来扰乱行为反应10,11。我们的结果表明避蚊胺在广泛不同的分类群中的有效性具有一致的主题：对多个化学感应神经元的影响，破坏气味刺激和行为反应之间的配对。避蚊胺选择性干扰秀丽隐杆线虫线虫的趋化性和 str-217 突变基因或表达它的一对化学感应神经元的沉默使蠕虫对避蚊胺具有抗性。

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A natural variant and engineered mutation in a GPCR promote DEET resistance in C. elegans

DEET (N,N-diethyl-meta-toluamide) is a synthetic chemical identified by the US Department of Agriculture in 1946 in a screen for repellents to protect soldiers from mosquito-borne diseases1,2. Since its discovery, DEET has become the world’s most widely used arthropod repellent and is effective against invertebrates separated by millions of years of evolution—including biting flies3, honeybees4, ticks5, and land leeches3. In insects, DEET acts on the olfactory system5–12 and requires the olfactory receptor co-receptor Orco7,9–12, but exactly how it works remains controversial13. Here we show that the nematode Caenorhabditis elegans is sensitive to DEET and use this genetically tractable animal to study the mechanism of action of this chemical. We found that DEET is not a volatile repellent, but instead interferes selectively with chemotaxis to a variety of attractant and repellent molecules. In a forward genetic screen for DEET-resistant worms, we identified a gene that encodes a single G protein-coupled receptor, str-217, which is expressed in a single pair of chemosensory neurons that are responsive to DEET, called ADL neurons. Mis-expression of str-217 in another chemosensory neuron conferred responses to DEET. Engineered str-217 mutants, and a wild isolate of C. elegans that carries a str-217 deletion, are resistant to DEET. We found that DEET can interfere with behaviour by inducing an increase in average pause length during locomotion, and show that this increase in pausing requires both str-217 and ADL neurons. Finally, we demonstrated that ADL neurons are activated by DEET and that optogenetic activation of ADL neurons increased average pause length. This is consistent with the ‘confusant’ hypothesis, which proposes that DEET is not a simple repellent but that it instead modulates multiple olfactory pathways to scramble behavioural responses10,11. Our results suggest a consistent motif in the effectiveness of DEET across widely divergent taxa: an effect on multiple chemosensory neurons that disrupts the pairing between odorant stimulus and behavioural response.DEET interferes selectively with chemotaxis of Caenorhabditis elegans nematodes, and mutations in the str-217 gene or silencing of the pair of chemosensory neurons that express it makes worms DEET-resistant.

更新日期：2018-09-26

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