Fatty Acid Biosynthesis in Cryptosporidium parvum

描述（由申请方提供）：微小隐孢子虫是一种单细胞病原体，可引起人类和动物严重水样腹泻。这种病原体可引起艾滋病患者的一种机会性感染，目前还没有完全有效的治疗方法。隐孢子虫也是一种重要的水和食源性病原体，并在NIH生物防御研究计划中被列为B类优先病原体之一。抗隐孢子虫药物治疗进展缓慢的主要原因是对隐孢子虫的基本代谢途径认识不足。在其他顶复门中发现的许多定义明确或有希望的药物靶点在C.小的因此，对该独特的C.了解和控制这种寄生虫需要parvum代谢途径。脂肪酸是所有细胞的基本成分之一。我们开创了C.小的我们目前的数据表明，C。小顶复门与其它顶复门的不同之处在于缺乏II型FAS及其相关的顶质体，并且依赖于三种不同的延长脂肪酸的途径（即I型模块脂肪酸合酶（CpFAS 1）、聚酮合酶（CpPKS 1）和长链脂肪酰基延长酶（CpLCE 1））。此外，我们已经确定了假定的主要组成部分，构成了高度精简的脂肪酸代谢，在C。小的这些进展现在使我们能够理性地剖析C的功能。脂肪酸代谢的详细研究。我们的长期目标是阐明C. parvum和探索这一途径作为一个合理的药物靶点。我们的假设是，参与C。脂肪酸代谢在结构和功能水平上与人类和动物中的对应物不同，可以作为合理的药物靶标。在本研究中，我们将着重研究C. 1）通过对CpFAS 1、CpPKS 1和膜相关脂肪酸延伸酶的功能分析，阐明了脂肪酸合成的分子机制。2)通过对酰基辅酶A转移酶和脂肪酰基辅酶A结合蛋白的功能分析，阐明脂肪酸活化和转运的分子机制。3)通过寻找隐孢子虫脂肪酸代谢酶的选择性抑制剂，验证脂肪酸代谢酶可作为合理的药物靶标。

DESCRIPTION (provided by applicant): Cryptosporidium parvum is a unicellular pathogen that can cause severe watery diarrhea in humans and animals. This pathogen can cause one of the opportunistic infections in AIDS patients for which no complete effective treatment is yet available. Cryptosporidium is also a significant water- and food-borne pathogen, and listed as one of the Category B priority pathogens in the NIH biodefense research program. The slow development of anti-cryptosporidiosis chemotherapy is primarily due to the poor understanding on the basic metabolic pathways in this parasite. Many well-defined or promising drug targets found in other apicomplexans are either absent or highly divergent in C. parvum. Therefore, detailed molecular and functional studies on the unique C. parvum metabolic pathways are needed for the understanding and control of this parasite. Fatty acids are one of the essential components in all cells. We have pioneered the research on the fatty acid synthesis in C. parvum. Our current data have revealed that C. parvum differs from other apicomplexans by lacking Type II FAS and its associated apicoplast, and relying on three distinct pathway for elongating fatty acids (i.e. a Type I modular fatty acid synthase (CpFAS1), a polyketide synthase (CpPKS1), and a long chain fatty acyl elongase (CpLCE1). In addition, we have identified putative major components that constitute the highly streamlined fatty acid metabolism in C. parvum. These advances now allow us to rationally dissect the function of C. parvum fatty acid metabolism in detail. Our long-term goal is to delineate the function(s) of major components constituting the fatty acid metabolism in C. parvum and to explore this pathway as a rational drug target. Our hypothesis is that major enzymes involved in the C. parvum fatty acid metabolism differ from their counterparts in humans and animals at both structural and functional levels, and may serve as rational drug targets. In this proposal, we will focus on studying different mechanisms governing fatty acid elongation and activation in C. parvum by achieving the following three specific aims: 1) To delineate the molecular machineries governing the fatty acid synthesis in the parasite by functional analyses of CpFAS1, CpPKS1 and a membrane-associated fatty acid elongase. 2) To elucidate the molecular mechanisms involved in the activation and transporting of fatty acids by functional analyses of acyl-CoA synthases and fatty acyl-CoA binding protein. 3) To validate that fatty acid metabolic enzymes may serve as rational drug target in Cryptosporidium by discovering inhibitors selectively against, parasite fatty acid metabolic enzymes.