Mechanisms of action and resistance of sodium channel-targeted insecticides

描述（由申请人提供）：本研究的长期目标是了解节肢动物害虫杀虫剂抗性的分子基础。作为许多人类病原体的携带者和/或室内过敏原的主要来源，节肢动物害虫，如蟑螂、蚊子和蜱虫，是对人类健康的主要威胁。控制这些节肢动物害虫的策略在很大程度上依赖于杀虫剂的使用，例如对电压门控钠通道起作用的拟除虫菊酯。然而，拟除虫菊酯的大量使用已导致世界范围内杀虫剂耐药性的迅速发展。抗性的一个主要机制是击倒抗性（knockdown resistance, kdr），它降低了神经元的敏感性，并对所有拟除虫菊酯类杀虫剂产生交叉抗性。近十年来的研究表明，钠通道基因的突变与多种节肢动物的kdr有关。我们最近的研究结果表明，拟除虫菊酯抗性有两种不同的机制：一种是通过减少拟除虫菊酯结合，另一种是通过改变门控特性。这些结果为假设驱动的研究奠定了关键阶段，以阐明拟除虫菊酯结合位点以及钠通道门控特性的改变如何导致拟除虫菊酯抗性。我们也开始研究一种新开发的杀虫剂——茚虫卡威的分子作用，它作用于钠通道的机制与拟除虫菊酯完全不同。本提案要检验的中心假设是，这两类杀虫剂与钠通道上不同的受体位点结合，并在外部配置中捕获不同的电压感应域，从而改变钠通道的功能。拟除虫菊酯主要与钠通道的结构域II相互作用，抑制通道失活，而茚虫威主要与结构域IV相互作用，促进通道失活。这一建议的三个具体目标是：1。基于自然发生的kdr突变和定点诱变的拟除虫菊酯结合的分子决定因素的综合分析。2. 确定由钠通道门控特性改变引起的拟除虫菊酯抗性的分子基础。3. 描述茚虫威对昆虫钠通道的分子作用。

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand the molecular basis of insecticide resistance in arthropod pests. As carriers of numerous human pathogens and/or a major source of indoor allergens, arthropod pests, such as cockroaches, mosquitoes and ticks, are major threats to human health. Strategies for the control of these arthropod pests rely heavily on the use of insecticides, such as pyrethroids which act on voltage-gated sodium channels. However, the intensive use of pyrethroids has led to rapid development of insecticide resistance worldwide. One major mechanism of resistance, knockdown resistance (kdr), reduces neuronal sensitivity and confers cross-resistance to all pyrethroid insecticides. Research in the past decade shows that mutations in the sodium channel gene are responsible for kdr in various arthropod pest species. Our recent findings indicate that there are two distinct mechanisms of pyrethroid resistance: one via reducing pyrethoid-binding and the other via altering gating properties. These results set a critical stage for hypothesis-driven research to elucidate the pyrethroid-binding site and how alterations of gating properties of sodium channels cause pyrethroid resistance. We have also begun to study the molecular action of a newly developed insecticide, indoxacarb, that acts on the sodium channel by a mechanism completely different from that of pyrethroids. The central hypothesis to be examined in this proposal is that these two classes of insecticides bind to distinct receptor sites on the sodium channel and trap distinct voltage-sensing domains in the outward configuration, modifying sodium channel function. Pyrethroids interact mainly with domain II of sodium channels, inhibiting channel deactivation, whereas indoxacarb interacts mainly with domain IV, promoting channel inactivation. The three specific aims of this proposal are: 1. Comprehensive analysis of the molecular determinants of pyrethroid-binding based on naturally occurring kdr mutations and site-directed mutagenesis. 2. Determine the molecular basis of pyrethroid resistance caused by alterations in sodium channel gating properties. 3. Characterize the molecular action of indoxacarb on the insect sodium channel.