Plasmodium falciparum utilizes pyrophosphate to fuel an essential proton pump in the ring stage and the transition to trophozoite stage.
Plasmodium falciparum utilizes pyrophosphate to fuel an essential proton pump in the ring stage and the transition to trophozoite stage.
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DOI：
10.1371/journal.ppat.1011818
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发表时间：
2023-12
期刊：
影响因子：
6.7
通讯作者：
中科院分区：
文献类型：
--
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在红细胞内的无性生长和复制周期中，恶性疟原虫主要依靠糖酵解来提供能量，因为它的单个核糖体很少或根本不进行氧化磷酸化。裂殖子侵入宿主红细胞后，环状期持续约20小时，传统上认为是代谢静止期。然而，最近的研究表明，环阶段在几个能量消耗过程中是活跃的，包括基因转录，蛋白质翻译，蛋白质输出和宿主细胞内的运动。目前还不清楚是否单独的低糖酵解通量可以满足入侵后长时间的环阶段的能量需求。在这里，我们证明了代谢副产物焦磷酸盐（PPi）是一个关键的能源发展的环阶段和过渡到滋养体阶段。在无性发育的早期阶段，寄生虫利用恶性疟原虫空泡焦磷酸酶1（PfVP 1），一个古老的焦磷酸盐驱动的质子泵，输出质子穿过寄生虫质膜。PfVP 1的条件性缺失导致持续近48小时的延迟的环阶段和寄生虫死亡开始之前的环到滋养体转变的完全阻断。这种发育停滞可以部分救出由拟南芥的orthopathic液泡焦磷酸酶，但不是由酿酒酵母，缺乏质子泵活性的可溶性焦磷酸酶。由于质子泵焦磷酸酶在人类宿主中已经进化丢失，PfVP 1的重要性表明其作为抗疟疾药物靶标的潜力。非常需要环阶段的药物靶标，因为目前的抗疟药对该阶段的效力有限。膜结合质子泵焦磷酸酶（H+-PPases），也称为液泡焦磷酸酶（V-PPases），是由焦磷酸盐（PPi）而不是ATP水解提供动力的单亚基质子泵。这些古老的、ATP独立的质子泵在细菌、古生菌、植物和原生生物中进化保守，但在真菌和动物中不存在。而H+-PPases在疟原虫属（Plasmodium spp.）20年前，它们在疟疾寄生虫中的意义仍然不清楚。在这项研究中，我们已经揭示了PfVP 1，恶性疟原虫空泡焦磷酸酶1，在无性发育周期的早期阶段，包括环阶段和环滋养体过渡的关键作用。通过多种方法，我们已经证实PfVP 1是恶性疟原虫中的PPi水解质子泵，这首次表明PPi在疟原虫中作为能量来源。我们的研究结果进一步表明，PfVP 1是一个很好的抗疟药物靶点，因为它的基本生理作用和它在人类宿主中的缺乏。靶向环期的抗疟药是非常需要的，因为大多数药物对这个代谢不太活跃的阶段的疗效有限。
During asexual growth and replication cycles inside red blood cells, the malaria parasite Plasmodium falciparum primarily relies on glycolysis for energy supply, as its single mitochondrion performs little or no oxidative phosphorylation. Post merozoite invasion of a host red blood cell, the ring stage lasts approximately 20 hours and was traditionally thought to be metabolically quiescent. However, recent studies have shown that the ring stage is active in several energy-costly processes, including gene transcription, protein translation, protein export, and movement inside the host cell. It has remained unclear whether a low glycolytic flux alone can meet the energy demand of the ring stage over a long period post invasion. Here, we demonstrate that the metabolic by-product pyrophosphate (PPi) is a critical energy source for the development of the ring stage and its transition to the trophozoite stage. During early phases of the asexual development, the parasite utilizes Plasmodium falciparum vacuolar pyrophosphatase 1 (PfVP1), an ancient pyrophosphate-driven proton pump, to export protons across the parasite plasma membrane. Conditional deletion of PfVP1 leads to a delayed ring stage that lasts nearly 48 hours and a complete blockage of the ring-to-trophozoite transition before the onset of parasite death. This developmental arrest can be partially rescued by an orthologous vacuolar pyrophosphatase from Arabidopsis thaliana, but not by the soluble pyrophosphatase from Saccharomyces cerevisiae, which lacks proton pumping activities. Since proton-pumping pyrophosphatases have been evolutionarily lost in human hosts, the essentiality of PfVP1 suggests its potential as an antimalarial drug target. A drug target of the ring stage is highly desired, as current antimalarials have limited efficacy against this stage. Membrane-bound proton pumping pyrophosphatases (H+-PPases), also known as vacuolar pyrophosphatases (V-PPases), are single-subunit proton pumps powered by hydrolysis of pyrophosphate (PPi) rather than ATP. These ancient, ATP independent proton pumps have been evolutionarily conserved in bacteria, archaea, plants, and protists, but are absent in fungi and animals. While H+-PPases were discovered in Plasmodium spp. 20 years ago, their significance in malaria parasites has remained unclear. In this study, we have unveiled the pivotal roles of PfVP1, Plasmodium falciparum vacuolar pyrophosphatase 1, in the early phases of the asexual developmental cycle, including the ring stage and the ring-to-trophozoite transition. Through multiple approaches, we have confirmed that PfVP1 is a PPi hydrolyzing proton pump in P. falciparum, indicating, for the first time, that PPi serves as an energy source in malaria parasites. Our results further indicate that PfVP1 is an excellent antimalarial drug target due to its essential physiological roles and its absence in the human hosts. Antimalarials targeting the ring stage are highly desired, as most drugs have limited efficacy against this metabolically less active stage.
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