Roles of Lipoate Pathways in Plasmodium Survival

描述(申请人提供)：疟疾寄生虫每年造成3亿-5亿人感染和200万-300万人死亡。在红细胞的无性发育阶段，寄生虫从人类血清中获取某些营养物质，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关键酶辅因子及其在恶性疟原虫中的代谢。我们最近的研究表明，疟疾寄生虫包含一条从脂肪酸生物合成的中间产物重新合成脂酸盐的代谢途径，以及从人血清中清除脂酸盐的两种机制。这些途径似乎存在于寄生虫的不同亚细胞室中，可能是独立的，对寄生虫的生存是必不可少的。拟议的研究将使用生化、细胞生物学和遗传学方法来研究这些未知的途径，并确定合成和宿主来源的脂酸盐在寄生虫生存中的作用。具体目标1将确定恶性疟原虫脂酸盐生物合成机制的活动和组织，以及合成脂酸盐在寄生虫生存中的作用。具体目标2将确定外源性脂酸盐在寄生虫生存中的作用，它在寄生虫中的分布，以及恶性疟原虫脂酸盐清除途径的活动和组织。这些研究可以确定疟疾寄生虫的质膜细胞器和线粒体之间存在细胞内代谢物运输途径。或者，这些研究可以证明，尽管存在脂肪酸盐生物合成途径，但恶性疟原虫对脂肪酸盐具有营养缺陷性。负责脂类代谢的蛋白质最终可能被证明是治疗干预的有吸引力的目标--特别是因为抑制剂可以与已知的恶性疟原虫脂肪酸生物合成抑制剂协同作用。

DESCRIPTION (provided by applicant): Malaria parasites are responsible for 300-500 million infections and 2-3 million deaths annually. During the asexual stages of development in red blood cells, 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 indicate that malaria parasites contain a metabolic pathway to synthesize lipoate de novo from intermediates of fatty acid biosynthesis as well as two mechanisms for scavenging lipoate from human serum. These pathways appear to reside in different subcellular compartments in the parasite and may be independent and essential for parasite survival. The proposed studies will employ biochemical, cell biology and genetic approaches to investigate these unexplored pathways and establish the roles of synthesized and host-derived lipoate in parasite survival. Specific Aim 1 will define the activities and organization of the P. falciparum lipoate biosynthetic machinery and the role of synthesized lipoate in parasite survival. Specific Aim 2 will define the role of exogenous lipoate in parasite survival, its distribution in the parasite, and the activities and organization of the P. falciparum lipoate scavenging pathways. These studies could establish the existence of an intracellular metabolite trafficking pathway between the apicoplast organelle and the mitochondrion of malaria parasites. Alternatively, these studies could demonstrate that P. falciparum parasites are auxotrophic for lipoate despite the existence of a lipoate biosynthetic pathway. Proteins responsible for the metabolism of lipoate may ultimately prove to be attractive targets for therapeutic intervention - especially since inhibitors could act synergistically with known inhibitors of P. falciparum fatty acid biosynthesis.