The suf iron-sulfur cluster synthesis pathway is required for apicoplast maintenance in malaria parasites.
The suf iron-sulfur cluster synthesis pathway is required for apicoplast maintenance in malaria parasites.
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DOI：
10.1371/journal.ppat.1003655
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发表时间：
2013
期刊：
影响因子：
6.7
通讯作者：
Prigge ST
中科院分区：
文献类型：
--
作者：
Gisselberg JE;Dellibovi-Ragheb TA;Matthews KA;Bosch G;Prigge ST
恶性疟原虫的顶体细胞器含有对肝期和血期发育至关重要的代谢途径。在血液阶段，缺乏质外体的寄生虫可以在异戊烯基焦磷酸(IPP)的存在下生长，这表明类异戊二烯是质外体中唯一需要的代谢物。有两种类异戊二烯生物合成酶被预测依赖于铁硫(FeS)簇辅助因子，然而，关于寄生虫中FES簇的合成或FES簇蛋白在寄生虫生物学中所起的作用，人们知之甚少。我们研究了两条可能的FeS团簇合成途径(ISC和SuF)，重点研究了硫获取的初始步骤。在其他真核生物中，这些蛋白质可以定位在多个亚细胞室中，增加了途径之间或冗余功能之间串扰的可能性。在恶性疟原虫中，SufS及其伴侣Sufe仅存在于质外体中，互补实验表明SufS具有半胱氨酸脱硫酶活性。ISCS及其效应子Isd11仅为线粒体，提示ISC途径不能参与质外体FES簇的合成。Suf途径被显性负性突变体破坏，导致只有在补充IPP时才能存活的寄生虫。这些寄生虫缺乏顶体细胞器及其细胞器基因组--当异戊二烯类生物合成被磷霉素特异性抑制时，没有观察到这一表型。综上所述，这些结果表明，Suf途径对于寄生虫的生存是必不可少的，除了在类异戊二烯的生物合成中发挥任何作用外，它在维持顶生质体细胞器方面也具有基础作用。铁是血液期恶性疟原虫生存所必需的，主要用于合成铁硫(FeS)簇辅助因子。我们调查了(FES)簇在疟疾寄生虫中所起的作用。我们证明了FeS簇的合成是在两个细胞器之间分配的：ISC途径是线粒体的，而Suf途径只在顶生质体细胞器中发现。只有在寄生虫培养中添加类异戊二烯产物时，通过显性否定方法干扰Suf途径的尝试才能成功。这一结果表明，类异戊二烯的生物合成依赖于功能上的Suf途径。出乎意料的是，我们还观察到，当我们中断Suf途径时，质外体细胞器完全丧失。这种表型不是由于抑制类异戊二烯的生物合成所致；我们用高水平的类异戊二烯抑制剂福米霉素处理寄生虫，而没有任何质外体细胞器的损失。这些结果表明，除了在类异戊二烯生物合成中的任何作用外，Suf途径在维持质外体细胞器方面也具有基础作用。抑制人类没有的Suf途径将阻止疟疾寄生虫的生长。
The apicoplast organelle of the malaria parasite Plasmodium falciparum contains metabolic pathways critical for liver-stage and blood-stage development. During the blood stages, parasites lacking an apicoplast can grow in the presence of isopentenyl pyrophosphate (IPP), demonstrating that isoprenoids are the only metabolites produced in the apicoplast which are needed outside of the organelle. Two of the isoprenoid biosynthesis enzymes are predicted to rely on iron-sulfur (FeS) cluster cofactors, however, little is known about FeS cluster synthesis in the parasite or the roles that FeS cluster proteins play in parasite biology. We investigated two putative FeS cluster synthesis pathways (Isc and Suf) focusing on the initial step of sulfur acquisition. In other eukaryotes, these proteins can be located in multiple subcellular compartments, raising the possibility of cross-talk between the pathways or redundant functions. In P. falciparum, SufS and its partner SufE were found exclusively the apicoplast and SufS was shown to have cysteine desulfurase activity in a complementation assay. IscS and its effector Isd11 were solely mitochondrial, suggesting that the Isc pathway cannot contribute to apicoplast FeS cluster synthesis. The Suf pathway was disrupted with a dominant negative mutant resulting in parasites that were only viable when supplemented with IPP. These parasites lacked the apicoplast organelle and its organellar genome – a phenotype not observed when isoprenoid biosynthesis was specifically inhibited with fosmidomycin. Taken together, these results demonstrate that the Suf pathway is essential for parasite survival and has a fundamental role in maintaining the apicoplast organelle in addition to any role in isoprenoid biosynthesis. Iron is essential for the survival of blood stage P. falciparum and is used primarily in the synthesis of iron-sulfur (FeS) cluster cofactors. We investigated the role that (FeS) clusters play in malaria parasites. We demonstrated that the synthesis of FeS clusters is partitioned between two organelles: the Isc pathway is mitochondrial while the Suf pathway is found exclusively in the apicoplast organelle. Attempts to interfere with the Suf pathway through a dominant negative approach were only successful when parasite cultures were supplemented with an isoprenoid product. This result demonstrates that isoprenoid biosynthesis depends on a functional Suf pathway. Unexpectedly, we also observed the complete loss of the apicoplast organelle when we disrupted the Suf pathway. This phenotype does not result from inhibition of isoprenoid biosynthesis; we treated parasites with high levels of the isoprenoid inhibitor fosmidomycin without any loss of the apicoplast organelle. These results demonstrate that the Suf pathway has a fundamental role in maintaining the apicoplast organelle in addition to any role in isoprenoid biosynthesis. Inhibition of the Suf pathway, which is not found in humans, will block the growth of malaria parasites.
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