Mosquitocidal Action of Bacillus thuringensis Toxins

苏云金芽孢杆菌毒素的杀蚊作用

• 批准号: 8294971
• 负责人: Sarjeet S Gill
• 金额: $ 48.06万
• 依托单位: UNIVERSITY OF CALIFORNIA RIVERSIDE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8294971
• 关键词: Aedes; Affinity; Alkaline Phosphatase; Amino Acids; Aminopeptidase; Anopheles Genus; Bacillus (bacterium); Bacillus thuringiensis; Binding; Brazil; C-terminal; Cadherins; Cell membrane; Characteristics; China; Collaborations; Country; Crying; Culex (Genus); Culicidae; Data; Disease Vectors; Elements; France; Grant; Health; Human; India; Individual; Insecta; Investigation; Knowledge; Laboratories; Larva; Mediating; Membrane; Methods; Midgut; Modeling; Moths; Play; Proteins; Research; Research Personnel; Resistance; Resistance development; Resources; Role; Scheme; Simuliidae; Simulium genus; Targeted Toxins; Testing; Toxic effect; Toxin; base; cadherin-6; human disease; in vivo; mosquitocidal; novel; public health relevance; receptor; synergism

DESCRIPTION (provided by applicant): Bacillus thuringiensis subsp. israelensis (Bti) has been used in the field for over twenty years without resistance development in any target insect. In contrast, mosquito resistance to B. sphaericus has been observed in the field in many countries. This remarkable difference in the propensity to develop resistance to two mosquitocidal Bacillus strains is likely due to the presence of multiple toxins in Bti. However, mosquitoes are able to rapidly develop resistance to individual toxins from this strain. A major reason for the apparent inability of mosquitoes to develop resistance to Bti is the presence of cytolytic (Cyt) toxins in this and other mosquitocidal strains. During the last grant period we showed that key to the lack of mosquito resistance to Bti was how two toxins in this strain, namely Cry11A and Cyt1A toxins interact. We showed Cyt1A acts as a surrogate receptor for Cry11Aa. Importantly Cyt1Aa binds through Cry11A loop domains that are also involved in binding endogenous Aedes aegypti receptor proteins. Our research showed Aedes receptor proteins include cadherin, alkaline phosphatases (ALP), and aminopeptidases (APNs). All three classes bind mosquitocidal toxins with relatively high affinity, unlike in lepidopterans where only cadherin binds with high affinity. This implies both APN and ALP of mosquitoes could act as primary rather than as secondary receptors as in moths, suggesting a possible difference in the mode of action of mosquitocidal and lepidopteran Cry toxins. We believe however, there is conservation in the mode of action of Bt Cry toxins. Therefore we hypothesize a similar mode of action of action occurs in mosquitoes as in lepidopterans. In this proposal we plan to test this hypothesis. Consequently, we hypothesize that: (i) cadherin is a key protein which mediates initial binding to mosquitocidal Cry toxins and is essential for larval toxicity; ii) ALPs (and APNs) act as secondary receptors that allow toxin targeting to the cell membrane. Also in the previous proposal we showed Cyt1A plays a critical role in acting as a surrogate receptor for Cry11Aa. We therefore hypothesize that (iii) Cyt1A also is a receptor for other Cry toxins in Bti, and synergizes the toxicity of mosquitocidal Cry toxins. We will test this hypothesis and also elucidate the mechanism by which Cyt toxins insert into the membrane to act as surrogate receptors. This project is also a proposal to continue a successful collaboration between three different investigators to best use the expertise of each laboratory. PUBLIC HEALTH RELEVANCE: B. thuringiensis subsp. israelensis are used for control of human disease vectors, such as species of Simulium, Aedes, Culex, and Anopheles. Elucidating mechanisms of Cry toxin action in aids our understanding of how mosquito and black fly control is achieved and also enables us to determine mechanisms by which resistance can occur. This mode of Cyt1A toxin action investigation also illuminates mechanism of synergism between mosquitocidal Cry and Cyt toxins. Finally, elucidation of mechanisms by which the Cyt1Aa toxin acts also will help us understand how other cytolytic toxins of human health significance cause toxicity.

描述（由申请人提供）：苏云金芽孢杆菌亚种。 israelensis (Bti) 已在田间使用二十多年，没有在任何目标昆虫中产生抗药性。相比之下，许多国家在实地观察到蚊子对球形芽孢杆菌具有抗药性。对两种杀蚊芽孢杆菌菌株产生抗药性的这种显着差异可能是由于 Bti 中存在多种毒素。然而，蚊子能够迅速对这种菌株的个别毒素产生抵抗力。蚊子明显无法对 Bti 产生抗药性的一个主要原因是该杀蚊菌株和其他杀蚊菌株中存在细胞溶解 (Cyt) 毒素。在上一次资助期间，我们发现蚊子对 Bti 缺乏抗性的关键在于该菌株中的两种毒素（即 Cry11A 和 Cyt1A 毒素）如何相互作用。我们证明 Cyt1A 作为 Cry11Aa 的替代受体。重要的是，Cyt1Aa 通过 Cry11A 环结构域结合，Cry11A 环结构域也参与结合内源埃及伊蚊受体蛋白。我们的研究表明伊蚊受体蛋白包括钙粘蛋白、碱性磷酸酶 (ALP) 和氨肽酶 (APN)。所有这三类都以相对高的亲和力结合杀蚊毒素，这与鳞翅目动物不同，在鳞翅目动物中，只有钙粘蛋白以高亲和力结合。这意味着蚊子的 APN 和 ALP 可以作为主要受体，而不是像飞蛾那样作为次要受体，这表明杀蚊剂和鳞翅目 Cry 毒素的作用方式可能存在差异。然而，我们相信 Bt Cry 毒素的作用方式是保守的。因此，我们假设蚊子中发生与鳞翅目动物类似的作用模式。在本提案中，我们计划检验这一假设。因此，我们假设：（i）钙粘蛋白是介导与杀蚊剂 Cry 毒素的初始结合的关键蛋白，并且对于幼虫毒性至关重要； ii) ALP（和 APN）作为二级受体，允许毒素靶向细胞膜。同样在之前的提案中，我们表明 Cyt1A 在作为 Cry11Aa 的替代受体方面发挥着关键作用。因此，我们假设 (iii) Cyt1A 也是 Bti 中其他 Cry 毒素的受体，并协同杀蚊 Cry 毒素的毒性。我们将检验这一假设，并阐明细胞色素毒素插入膜以充当替代受体的机制。该项目还提议继续三个不同研究人员之间的成功合作，以最好地利用每个实验室的专业知识。 公共卫生相关性：苏云金芽孢杆菌亚种。 israelensis 用于控制人类疾病媒介，例如蝽、伊蚊、库蚊和按蚊。阐明 Cry 毒素的作用机制有助于我们了解如何实现蚊子和黑蝇的控制，并使我们能够确定产生耐药性的机制。这种 Cyt1A 毒素作用研究模式也阐明了 Cry 杀蚊剂和 Cyt 毒素之间的协同机制。最后，阐明 Cyt1Aa 毒素的作用机制也将帮助我们了解其他对人类健康具有重要意义的细胞溶解毒素如何引起毒性。