A new target for malaria drug development

描述（由申请人提供）：疟疾是媒介传播的疾病，每年在全世界感染2亿至3亿人。它是由疟原虫属的四种单细胞寄生虫中的任何一种感染红细胞引起的。当由恶性疟原虫引起时，疟疾是威胁生命的，导致100万至200万人死亡，主要是幼儿。目前的治疗方法受到寄生虫耐药性增加的影响，开发疫苗的努力受到疟原虫生命周期的严重限制;因此，需要新的治疗方法。最致命的疟疾寄生虫，恶性疟原虫，最近测序的基因组，揭示了两个腺苷酸环化酶基因（PfACs）相关的碳酸氢盐响应可溶性腺苷酸环化酶（SAC）在哺乳动物和蓝藻。他们的序列预测PfAC是碳酸氢盐响应性的，并且我们假设至少有一个是疟原虫绝对依赖于高水平的二氧化碳/碳酸氢盐的生存能力的原因。因此，PfAC可能是抗疟药物的新靶点。我们用我们开发的小分子（KH 7）治疗恶性疟原虫，该小分子抑制迄今为止测试的所有sAC样环化酶，包括在哺乳动物、单细胞真核生物和细菌中发现的sAC样环化酶。在单个细胞周期内，KH 7以剂量依赖性方式杀死在红细胞中培养的寄生虫。一种对sAC样环化酶呈惰性的结构相关化合物（KH7.15）对寄生虫生长没有影响。在这项授权申请中，我们建议克隆和表征这两种PfAC环化酶，并确认它们是否是KH 7致死性的靶标。如果PfAC被验证为新的抗疟药物的靶点，我们建议使用纯化的疟原虫环化酶来筛选化学文库，以鉴定相对于人类SAC对疟原虫环化酶具有选择性的化合物。

DESCRIPTION (provided by applicant): Malaria is vector-borne disease infecting 200-300 million people per year worldwide. It is caused by infection of red blood cells by any one of four unicellular parasites from the genus Plasmodium. When caused by Plasmodium falciparum, malaria is life threatening, resulting in 1-2 million deaths, primarily in young children. Current treatments suffer from increasing resistance among parasites and efforts to develop a vaccine are severely limited by the Plasmodium life cycle; therefore, new treatments are needed. The recently sequenced genome of the most lethal malarial parasite, Plasmodium falciparum, revealed two adenylyl cyclase genes (PfACs) related to the bicarbonate responsive soluble adenylyl cyclases (sAC) in mammals and cyanobacteria. Their sequences predict the PfACs to be bicarbonate responsive, and we hypothesized that at least one is responsible for Plasmodium's absolute dependence on high levels of carbon dioxide/bicarbonate for viability. Therefore, the PfACs may represent new targets for an antimalarial drug. We treated P. falciparum with a small molecule (KH7) we developed which inhibits all sAC-like cyclases tested thus far, including sAC-like cyclases found in mammals, unicellular eukaryotes and bacteria. Parasites cultured in red blood cells were killed by KH7 in a dose dependent manner within a single cell cycle. A structurally related compound (KH7.15) which is inert towards sAC-like cyclases had no effect on parasite growth. In this grant application, we propose to clone and characterized the two PfAC cyclases and confirm whether they are the target of KH7 lethality. If the PfACs are validated as targets for new antimalarial drugs, we propose to use purified Plasmodium cyclases to screen a chemical library to identify compounds selective for Plasmodium cyclases relative to human sAC.