Abscisic acid synthesis and role in dormancy of malaria

 描述（申请人提供）：疟疾，由疟原虫属引起的传染病。仍然是世界范围内的一个主要问题，部分原因是治疗方面的挑战，如治疗后耐药性增加和寄生虫复发。这可能部分由休眠机制解释，休眠机制允许寄生虫逃避压力，例如当前抗疟疾治疗引起的压力。药物诱导的休眠涉及寄生虫进入低代谢活动状态，其中感染可能似乎已被清除，但当寄生虫恢复正常生长时会复发。目前，寄生虫如何能够调节休眠和复发的分子基础还不清楚。我们相信脱落酸（阿坝），类胡萝卜素的分解代谢产物，在植物种子休眠中具有良好的作用，可能会回答这些问题。 疟原虫中阿坝的合成需要顶质体，这是一种最初通过与红藻的次级内共生关系获得的细胞器。顶质体作为类异戊二烯生物合成的位点，产生焦磷酸异戊酯（IPP），其对于许多代谢过程是必需的，并且作为类胡萝卜素生物合成的前体。在这项研究中，我们发现了阿坝的存在下，红细胞阶段的恶性疟原虫使用气相色谱质谱（GC-MS）检测和量化阿坝水平的甲基化寄生虫提取物暴露于不同的类胡萝卜素抑制剂和apicoplast靶向抗生素。我们的初步数据检测到阿坝，发现当暴露于这些药物时，它会显着降低。在体外诱导休眠与双氢青蒿素，寄生虫观察到恢复生长较早时补充阿坝。我们还发现，fluridone（FLD），一个有效的阿坝生物合成抑制剂，导致生长延迟在正常的寄生虫生活周期，延长休眠的长度。 我们推测阿坝作为一种应激传感器，有助于调节恶性疟原虫的休眠。在这项研究中，我们的目标是表征阿坝的生物合成途径，使用一种创新的方法与13 C标记的前体，遵循纳入阿坝和中间体。我们还将进一步阐明阿坝在使用双氢青蒿素和抗叶酸药物诱导的休眠中的作用。我们的研究策略，其中包括采取一种新的方法，利用植物和寄生虫之间的进化联系，应有助于我们扩大我们的寄生虫药物逃避的理解，并对抗疟药的发展产生影响。

 DESCRIPTION (provided by applicant): Malaria, the infectious disease caused by Plasmodium spp. remains a major problem worldwide due in part to treatment challenges such as increasing drug resistance and parasite recrudescence following treatment. This may be partially explained by dormancy, a mechanism that allows the parasite to escape stress such as that induced by current antimalarial treatments. Drug-induced dormancy involves the parasite entering a state of low metabolic activity, where infection may appear to have been cleared, but recrudescence occurs when parasites resume normal growth. Currently, the molecular basis for how the parasite is able to regulate dormancy and recrudescence is not well understood. We believe that abscisic acid (ABA), a carotenoid catabolite with a well established role in seed dormancy in plants, may answer some of these questions. ABA synthesis in Plasmodium requires the apicoplast, an organelle that was originally obtained via a secondary endosymbiotic relationship with red algae. The apicoplast serves as the site for isoprenoid biosynthesis, producing isopentyl pyrophosphate (IPP), which is essential for a number of metabolic processes and serves as the precursor for carotenoid biosynthesis. In this study, we discovered the presence of ABA in the erythrocytic stages of P. falciparum using gas chromatography mass spectroscopy (GC-MS) to detect and quantify ABA levels in methylated parasitic extracts exposed to different carotenoid inhibitors and apicoplast-targeting antibiotics. Our preliminary data detected ABA and found it to be significantly decreased when exposed to these drugs. Following in vitro induction of dormancy with dihydroartemesinin, parasites were observed to resume growth earlier when supplemented with ABA. We also found that fluridone (FLD), a potent inhibitor of ABA biosynthesis, causes growth delay in the normal parasite life cycle and extends the length of dormancy. We hypothesize that ABA acts as a stress sensor that helps regulate dormancy in P. falciparum. In this study, we aim to characterize the biosynthetic pathway of ABA using an innovative approach with 13C labeled precursors to follow incorporation into ABA and intermediates. We will also further elucidate the role that ABA has in drug induced dormancy using dihydroartemesinin and antifolate drugs. Our research strategy, which involves taking a novel approach by utilizing the evolutionary link between plants and parasites should help us broaden our understanding of parasite drug evasion and have an impact on development of antimalarials.