Plasmepsin X function in Plasmodium

项目摘要/摘要 疟疾困扰着数亿人，每个人死于60多万人 去年，主要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 感兴趣的抗疟疾靶标。大量的天冬氨酸蛋白酶抑制剂 已经开发出在培养中对寄生虫有效的药物，但它们的特异性 目标一直难以捉摸。纤溶酶X(PMX)是最不典型的 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 新近发现PMX是红细胞内寄生虫排出和释放的关键酶 入侵。它激活主触发类枯草杆菌蛋白水解酶1(SUB1)， 启动蛋白质分解事件，使裂殖子走出宿主的红血 细胞(RBC)和侵袭新鲜红细胞。我们已经鉴定出一类天冬氨酸 一种被称为氨基海因的蛋白酶抑制剂，它似乎通过 PMX阻断，阻止SUB1激活，损害出口/侵袭。PMX 击倒表观复制抑制作用。其中一种抑制剂具有良好的 在啮齿动物疟疾模型中的药代动力学特性和口服治疗。我们 相信PMX是一个令人兴奋的新药靶点，但需要更好地表征其 为正在进行的药物开发提供信息并增强我们对 寄生虫生物学。 为了解决这些问题，目标1将研究PMX的特殊性，并将 解决了PMX是否直接使SUB1成熟的问题。生化 以SUB1为底物的分离PMX与随机多肽的检测 库将被执行。目标2将重点放在PMX与什么交互。是SUB1 唯一的底物？分泌囊中还有什么叫做外显子， PMX和SUB1都在哪里？目标3将解决PMX如何 它自身就会被激活。我们的初步数据表明，一定有 上游酶。我们将对加工过程进行表征，并寻找成熟酶。 我们预期拟议的研究将对 疟疾的发病机制，并将为治疗疟疾的新疗法指明方向 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.