CELL CYCLE OF PLASMODIUM FALCIPARUM

恶性疟原虫是人类疟疾的病原体，在蚊子和人类宿主体内的整个生命周期中经历了明显的形态变化。在红细胞内的生命周期中，寄生虫通过经历多轮DNA复制而偏离真核细胞周期的范例，并从单个细胞形成8至32个裂殖子。对调节疟疾寄生虫不寻常的红细胞发育阶段的生化变化和分子开关的清楚了解尚未建立。这项研究的长期目标是开发一种在恶性疟原虫红细胞内发育阶段细胞周期调节的模型。恶性疟原虫DNA合成启动的确切时机以及S期与有丝分裂之间的关系以及参与细胞周期进程的蛋白质的同一性和调控方式等尚不清楚。我们实验室最近的研究已经确定了一些分子工具来启动对恶性疟原虫细胞周期调控的深入研究。具体来说，我们建议进行以下工作：(A)为了鉴定和鉴定恶性疟原虫复制前复合体的组成成分，我们将首先关注恶性疟原虫MCM4、ORC1和ORC5同源物的细胞周期调控表达、细胞内定位和磷酸化的变化。(B)通过噬菌体相互作用克隆、lambda筛选文库的磷酸化筛选和双杂交筛选，鉴定与恶性疟原虫CDK样蛋白、CDK激活蛋白和复制前复合体成分相互作用的蛋白。(C)开发更有效的寄生虫细胞周期同步方法。通过对恶性疟原虫细胞周期调控因子的详细分析，可以深入了解恶性疟原虫分裂过程中异常无性分裂的分子机制。此外，参与细胞周期进程的酶有可能成为药物开发的有吸引力的靶点，特别是考虑到寄生虫和宿主的细胞周期调节之间的差异可能允许在指导针对寄生虫的治疗时具有一定程度的特异性。

Plasmodium falciparum, the causative agent of human malaria, undergoes distinct morphological changes during the progression through its life cycle in the mosquito and human hosts. During the intraerythrocytic life cycle, the parasite diverges from the paradigm of eukaryotic cell cycle by undergoing multiple rounds of DNA replication and forms 8 to 32 merozoites from a single cell. A clear understanding of the biochemical changes and molecular switches that regulate the unusual erythrocytic developmental stages of the malaria parasite has not been established. The long-term goal of this research is to develop a model for cell cycle regulation in the intraerythrocytic stages of development of malaria parasite P. falciparum. The regulation of the precise timing of initiation of DNA synthesis and the relationship between S phase and mitosis during development in P. falciparum remains unclear, as does the identity of the proteins involved in cell cycle progression and how the are regulated. Recent research done in our laboratory has identified a few molecular tools to initiate an in-depth study of the cell cycle regulation of P. falciparum. Specifically, we propose to carry out the following: (a) To identify and characterize components of P. falciparum pre-replication complex, we will initially focus on cell cycle regulated changes in expression, intracellular localization, and phosphorylation of P. falciparum homologues of MCM4, ORC1 and ORC5. (b) Identify proteins interacting with P. falciparum CDK-like kinases, CDK- activating kinases and pre-replication complex components by phage- based interaction cloning, phosphorylation screen of a lambda screen library, and by two-hybrid screen. (c) Develop more effective means of cell cycle synchronization of the parasites. A detailed analysis of P. falciparum cell cycle regulators provide insight into the molecular mechanism of unusual asexual division during Plasmodium schizogony. Furthermore, enzymes involved in cell cycle progression have the potential to be attractive targets for drug development, especially given that differences between cell cycle regulation in parasite and host might permit a level of specificity in directing therapies against the parasite.