Plasmepsin X function in Plasmodium

项目总结/摘要 疟疾折磨着数亿人，每年造成60多万人死亡 这一年，大多数是撒哈拉以南非洲的儿童。天冬氨酸蛋白酶长期以来一直是 抗疟目标。大量的天冬氨酸蛋白酶抑制剂， 在培养中对寄生虫是有效的，但它们的特异性 目标一直难以捉摸。Plasmepsin X（PMX）是目前最不常见的 在无性红细胞内疟疾寄生虫中发现的天冬氨酸蛋白酶。我们有 最近发现PMX是红细胞内寄生虫排出的关键酶， 入侵它激活主触发因子枯草溶菌素样蛋白酶1（SUB1）， 启动蛋白水解作用，使裂殖子脱离宿主的红血， 红细胞（RBC）并侵入新鲜RBC。我们已经确定了一类天冬氨酸 一种叫做氨基乙内酰脲的蛋白酶抑制剂， PMX封锁，防止SUB1激活并削弱出口/入侵。PMX 敲低仿表型抑制剂作用。其中一种抑制剂具有有利的 药物动力学特性，并在啮齿动物疟疾模型中给予口服治疗。我们 我相信PMX是一个令人兴奋的新药物靶点，但需要更好地表征其 为正在进行的药物开发提供信息，并提高我们对 寄生生物学 为了解决这些问题，目标1将研究PMX的特异性，并将 解决SUB1通过PMX成熟是否是直接的问题。生化 使用分离的PMX与SUB1作为底物和与随机肽的测定 图书馆将进行。目标2将重点关注PMX与什么交互。是SUB1 唯一的基板？分泌囊泡中还有什么叫做外丝， PMX和SUB1都在哪里？目标3将解决PMX如何 自己被激活了。我们的初步数据表明， 上游酶我们将描述加工过程并寻找成熟酶。 我们预计，拟议的研究将产生很大的洞察力， 疟疾的发病机制，并将指出新的治疗方法， 毁灭性的疾病

PROJECT SUMMARY / ABSTRACT Malaria afflicts several hundred million and kills more than 600,000 people each year, mostly children in Sub-Saharan Africa. Aspartic proteases have long been antimalarial targets of interest. A large number of aspartic protease inhibitors that are potent against parasites in culture have been developed, but their specific targets have been elusive. Plasmepsin X (PMX) is one of the least characterized aspartic proteases found in asexual intraerythrocytic malaria parasites. We have recently found that PMX is a key enzyme for intraerythrocytic parasite egress and invasion. It activates the master trigger subtilysin-like protease 1 (SUB1), launching proteolytic events that allow merozoites to get out of the host red blood cell (RBC) and invade fresh RBCs. We have identified a class of aspartic protease inhibitors called aminohydantoins that appear to kill parasites through PMX blockade, preventing SUB1 activation and impairing egress/invasion. PMX knockdown phenocopies inhibitor action. One of the inhibitors has favorable pharmacokinetic properties and gives oral cure in a rodent malaria model. We believe that PMX is an exciting new drug target but need to better characterize its function to inform ongoing drug development and enhance our understanding of parasite biology. To address these questions, aim 1 will examine the specificity of PMX and will address the question of whether SUB1 maturation by PMX is direct. Biochemical assays using isolated PMX with SUB1 as a substrate and with a random peptide library will be performed. Aim 2 will focus on what PMX interacts with. Is SUB1 the only substrate? What else is in the secretory vesicle called the exoneme, where PMX and SUB1 both reside? Aim 3 will address the question of how PMX itself gets activated. Our preliminary data suggest that there must be an upstream enzyme. We will characterize the processing and look for a maturase. We anticipate that the proposed studies will yield great insight into the pathogenesis of malaria and will point the way to new therapies for this devastating disease.