Targeting Trypanosoma brucei S-adenosylmethionine decarboxylase in Drug Discovery

描述（由申请人提供）：非洲人类锥虫病（HAT），通常称为昏睡病，由单细胞寄生虫布鲁氏锥虫引起，通过受感染的采采蝇传播给人类。锥虫病对撒哈拉以南非洲许多人的健康产生深远影响。如果不及时治疗，它是致命的，目前的药物治疗是有问题的，因为毒性和新出现的耐药性。多胺生物合成途径是开发抗HAT药物的有效靶点，新出现的证据提供了一个令人信服的案例，s -腺苷蛋氨酸脱羧酶（AdoMetDC）是开发新的抗锥虫药物的极有希望的靶点。AdoMetDC催化从腐胺生产多胺亚精胺的限速步骤。哺乳动物AdoMetDC是一种同源二聚体，它使用丙酮基作为辅助因子来稳定AdoMet脱羧过程中形成的碳离子中间体。最近，我们的实验室证明了锥虫AdoMetDC是

DESCRIPTION (provided by applicant): Human African Trypanosomiasis (HAT), commonly called sleeping sickness, is caused by single-celled parasites, Trypanosoma brucei, which are transmitted to humans by infected tsetse flies. Trypanosomiasis has a profound impact on the health of a large number of people in sub-Saharan Africa. It is fatal if left untreated and current drug therapy is problematic because of toxicity and emerging resistance. The polyamine biosynthetic pathway is a validated target for the development of drugs against HAT and the emerging evidence provides a compelling case that S-adenosylmethionine decarboxylase (AdoMetDC) is a highly promising target for the development of new anti-trypanosomal agents. AdoMetDC catalyses the ratelimiting step in the production of the polyamine spermidine from putrescine. Mammalian AdoMetDC is a homodimer that uses a pyruvoyl group as a cofactor to stabilize the carbanion intermediate formed during the decarboxylation of AdoMet. Recently, our lab demonstrated that the trypanosomatid AdoMetDC is regulated by a unique mechanism, heterodimer formation with a catalytically dead AdoMetDC homolog. This protein, designated prozyme, forms a high-affinity heterodimer with AdoMetDC and increases its activity by >1,000-fold. Further we confirmed that the heterodimer is the functional enzyme in vivo. My primary goals are to elucidate the mechanisms that regulate the AdoMetDC activation by the prozyme and to identify and characterize novel AdoMetDC inhibitors essential for the development of new anti-trypanosomal drugs. In order to do that, I will first focus on the identification of crucial amino acid residues involved in the activation in an attempt to gain insights into the mechanism of allosteric regulation. Next I will characterize species differences in the activation of AdoMetDC by prozyme by comparing the T. brucei AdoMetDC/prozyme complex to the homologs from T. cruzi and L. donovani. Finally I will perform a high-throughput screen (HTS) of a small molecule compound library to identify novel inhibitors of T. brucei AdoMetDC and to test these for activity against cultured parasites. Upon completion of these studies I will have identified and validated a number of novel inhibitors of AdoMetDC for future lead optimization studies that may lead to the discovery of new, less toxic drugs for the treatment of HAT. Project Narrative: Human African Trypanosomiasis is a insect borne disease that is fatal if untreated, yet current drug therapies are toxic and difficult to administer. The work described in this proposal characterizes an essential enzyme that has unique features in the parasite, with the goal of developing new chemotherapeutic agents against this devastating disease.