Roles of lipoate pathways in Plasmodium survival

描述（由申请人提供）：疟原虫每年造成超过5亿疟疾病例。在红细胞的无性发育阶段，疟疾寄生虫从人血清中获得某些营养物质，同时保留合成其他营养物质的能力。我们正在研究一种称为脂酸盐的必需酶辅助因子及其在恶性疟原虫中的代谢。我们最近的研究表明，红细胞期寄生虫对脂酸盐缺乏营养，即使它们含有合成这种辅助因子的代谢途径。顶质体细胞器中的蛋白质依赖于脂酸盐合成，而寄生虫线粒体中的蛋白质依赖于清除，无法获得顶质体合成的脂酸盐。提出的研究主要集中在脂酸清除的两个方面，并采用生物化学，细胞生物学和遗传方法的结合。我们的第一个目标是确定脂酸盐是如何从外部环境中吸收并附着在寄生虫线粒体中的特定蛋白质上的。这些实验将确定脂酸盐摄取的限速步骤，并将在脂酸盐附着酶和它们的蛋白质底物之间建立详细的联系。我们的第二个目标是鉴定对寄生虫生存至关重要的脂酸依赖线粒体蛋白，并确定这些蛋白在寄生虫生物学中的作用。在其他生物体中，这些蛋白质形成大型多酶复合物，具有多种代谢和非代谢作用。我们的实验将剖析这些蛋白质的结构域结构，确定它们的活性，并确定它们在蛋白质复合物中的结合伙伴。遗传方法将确定脂蛋白代谢蛋白在血期寄生虫存活中的作用。由于依赖宿主营养物质，这些蛋白质代表了寄生虫生物学的一个脆弱方面，可以在几个层面上作为目标。

DESCRIPTION (provided by applicant): Plasmodium parasites are responsible for over half a billion malaria cases annually. During the asexual stages of development in red blood cells, malaria parasites acquire certain nutrients from human serum while retaining the ability to synthesize others. We are studying an essential enzyme cofactor called lipoate and its metabolism in Plasmodium falciparum. Our recent studies demonstrate that erythrocytic stage parasites are auxotrophic for lipoate, even though they contain a metabolic pathway to synthesize this cofactor. Proteins in the apicoplast organelle rely on lipoate synthesis while proteins in the parasite mitochondrion rely on scavenging and cannot obtain lipoate synthesized in the apicoplast. The proposed studies are focused on two aspects of lipoate scavenging and employ a combination of biochemical, cell biology and genetic approaches. Our first aim is to define how lipoate is taken up from the external environment and attached to specific proteins in the parasite mitochondrion. These experiments will identify rate limiting steps in the uptake of lipoate and they will forge a detailed link between the lipoate attachment enzymes and their protein substrates. Our second aim is to identify the lipoate-dependent mitochondrial proteins that are essential for parasite survival and determine the roles of these proteins in parasite biology. In other organisms, these proteins form large multi-enzyme complexes which can have a variety of metabolic and non-metabolic roles. Our experiments will dissect the domain structure of these proteins, determine their activities, and identify their binding partners in protein complexes. Genetic approaches will define the roles of lipoate metabolism proteins in the survival of blood stage parasites. By virtue of relying on a host nutrient, these proteins represent a vulnerable aspect of parasite biology which could be targeted at several levels.