Abscisic acid synthesis and role in dormancy of malaria

 描述(申请人提供)：疟疾，由疟原虫引起的传染病。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。这可能部分是由休眠来解释的，休眠是一种允许寄生虫逃避压力的机制，比如目前的抗疟疾治疗所产生的压力。药物诱导的休眠涉及寄生虫进入低代谢活动状态，在这种状态下感染似乎已经清除，但当寄生虫恢复正常生长时，就会复发。目前，这种寄生虫如何调节休眠和复发的分子基础还不是很清楚。我们认为，脱落酸(ABA)，一种在植物种子休眠中具有广泛作用的类胡萝卜素分解代谢物，可能会回答其中的一些问题。疟原虫ABA的合成需要顶体，这是一种细胞器，最初是通过与红藻的次级内生共生关系获得的。顶生质体是类异戊二烯生物合成的场所，产生焦磷酸异戊酯(IPP)，它是许多代谢过程中必不可少的，也是类胡萝卜素生物合成的前体。在这项研究中，我们发现ABA存在于恶性疟原虫的红细胞期，用气相色谱-质谱仪(GC-MS)来检测和定量不同类胡萝卜素抑制剂和质膜靶向抗生素作用下甲基化的寄生虫提取物中的ABA水平。我们的初步数据检测到了ABA，并发现当接触这些药物时，ABA显著降低。在体外用双氢青蒿素诱导休眠后，观察到当添加ABA时，寄生虫恢复生长的时间更早。我们还发现，ABA生物合成的有效抑制剂氟里酮(FLD)会导致正常寄生虫生活史中的生长延迟，并延长休眠时间。我们推测ABA作为一种压力感受器，帮助调节恶性疟原虫的休眠。在这项研究中，我们的目标是用一种创新的方法来表征ABA的生物合成途径，方法是用13C标记的前体跟随ABA和中间体的掺入。我们还将进一步阐明ABA在双氢青蒿素和抗叶酸药物诱导的药物休眠中的作用。我们的研究策略包括利用植物和寄生虫之间的进化联系采取一种新的方法，这应该有助于我们扩大对寄生虫药物逃避的理解，并对抗疟疾药物的开发产生影响。

 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.