TRYPTOPHAN METABOLISM IN MOSQUITOES

蚊子是重要的疾病媒介，负责传播许多病毒、细菌和寄生虫病，如疟疾、登革热、黄热病和丝虫病。疟疾是由疟原虫感染引起的，是一种毁灭性的疾病，全世界有多达5亿人受其影响，每年造成多达200万人死亡。耐药寄生虫和抗杀虫剂蚊子媒介的发展迫切要求开发新的和创新的蚊子或寄生虫控制策略。破坏蚊子或疟原虫正常发育所必需的生理生化过程是控制疟疾的一种方法。在埃及伊蚊中发现了一种新的转氨酶，这种转氨酶专门用于将色氨酸氧化过程中形成的具有化学活性和潜在毒性的3-羟基尿氨酸转氨化为稳定的黄嘌呤酸，这种酶在幼虫和成年雌性蚊子中受到严格调节，在吸血后具有高活性。我们最近的数据表明，黄嘌呤酸还能刺激疟原虫的配子发生，这表明这一途径可能在启动疟原虫在蚊子载体中的发育中起关键作用。这项研究的长期目标是全面了解蚊子载体中这种酶的调控途径和机制。本研究的具体目的是：(1)利用各种生物化学技术纯化和表征蚊子体内的3-羟基犬尿氨酸转氨酶；(2)利用各种分子技术研究蚊子发育过程中3-羟基犬尿氨酸转氨酶的遗传调控，包括从蚊子幼虫中制备cDNA文库，从文库中分离3-羟基犬尿氨酸转氨酶cDNA；研究3-羟基犬尿氨酸转氨酶在蚊子发育过程中的基因表达。（III）研究3-羟基犬尿氨酸在按蚊体内转化为黄嘌呤酸的转氨化途径。我们的假设是，这种转氨化途径对蚊子的正常发育至关重要，也可能在刺激疟原虫的发育中起关键作用；因此，了解其调控机制可能会对未来通过创新蚊子控制策略对媒介发育产生负面干扰的努力产生重大影响，也可能为开发通过中断蚊子媒介中疟原虫的配子体发生来控制疟疾寄生虫的新工具提供见解。

Mosquitoes are important disease vectors, responsible for transmission of numerous viral, bacterial and parasitic diseases, such as malaria, dengue fever, yellow fever, and filariasis. Malaria, caused by infection with species of Plasmodium, is a devastating, disease which affects up to 500 million people world-wide, killing as many as 2 million a year. The development of drug resistant parasites, and insecticide resistant mosquito vectors urgently demands that new and innovative mosquito or parasite control strategies be developed. Disruption of the required physio-biochemical processes that are necessary for the normal development of either mosquitoes or malaria parasites is one approach for malaria control. A novel transaminase that is specific for the transamination of a chemically reactive and potentially toxic 3-hydroxykynurenine, formed during tryptophan oxidation, to stable xanthurenic acid is identified in Aedes aegypti mosquitoes, and this enzyme is tightly regulated with high activity in larvae and adult females after a bloodmeal. Our recent data show that xanthurenic acid also stimulates gametogenesis of Plasmodium parasites, suggesting this pathway may play critical role in initiating Plasmodium development in mosquito vectors. The long term goal of this research is to achieve a full understanding of the pathways and mechanisms governing the regulation of this enzyme in mosquito vectors. The specific aims of the proposed research are (I) to purify and characterize the 3-hydroxykynurenine transaminase from mosquitoes by various biochemical techniques, (II) to initiate studies concerning the genetic regulation of this transaminase in mosquitoes during development with various molecular techniques, which includes preparation of a cDNA library from mosquito larvae, isolation of 3-hydroxykynurenine transaminase cDNA from the library, and study of gene expression of the 3-hydroxykynurenine transaminase in mosquitoes during development, and (III) to study the transamination pathway of 3-hydroxykynurenine to xanthurenic acid in Anopheles mosquitoes. Our hypotheses are that this transamination pathway is critical for the normal development of mosquitoes and also may play a critical role in stimulating Plasmodium development; consequently, understanding the mechanism controlling its regulation could have a significant impact on future efforts to negatively interfere with vector development through innovative mosquito control strategies and also may provide insight into developing novel tools for the control of malaria parasites by interrupting gametogenesis of Plasmodium in mosquito vectors.