Stage-Specific Changes in Plasmodium Metabolism Required for Differentiation and Adaptation to Different Host and Vector Environments

Abstract

Malaria parasites (Plasmodium spp.) encounter markedly different (nutritional) environments during their complex life cycles in the mosquito and human hosts. Adaptation to these different host niches is associated with a dramatic rewiring of metabolism, from a highly glycolytic metabolism in the asexual blood stages to increased dependence on tricarboxylic acid (TCA) metabolism in mosquito stages. Here we have used stable isotope labelling, targeted metabolomics and reverse genetics to map stage-specific changes in Plasmodium berghei carbon metabolism and determine the functional significance of these changes on parasite survival in the blood and mosquito stages. We show that glutamine serves as the predominant input into TCA metabolism in both asexual and sexual blood stages and is important for complete male gametogenesis. Glutamine catabolism, as well as key reactions in intermediary metabolism and CoA synthesis are also essential for ookinete to oocyst transition in the mosquito. These data extend our knowledge of Plasmodium metabolism and point towards possible targets for transmission-blocking intervention strategies. Furthermore, they highlight significant metabolic differences between Plasmodium species which are not easily anticipated based on genomics or transcriptomics studies and underline the importance of integration of metabolomics data with other platforms in order to better inform drug discovery and design.

Novel Plasmodium falciparum metabolic network reconstruction identifies shifts associated with clinical antimalarial resistance

“…We predict that inhibitors of fumarate transport or fumarate hydratase and malate dehydrogenase would specifically kill artemisinin resistant parasites, offering an example of enhanced metabolic flexibility of sensitive parasites and a potential artemisinin-combination therapy target. The TCA cycle is essential during the mosquito-stage of parasite development [61, 116], but not the blood-stage [60, 61]; this once again highlights the possibility that resistant parasites exhibit incomplete transition to the metabolic state most appropriate for nutrient-rich blood.

Fig. 5Artemisinin resistance displays unique metabolic weaknesses.

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Zygote morphogenesis but not the establishment of cell polarity in Plasmodium berghei is controlled by the small GTPase, RAB11A

“…The expression of the paralogous RAB11B in pclag::rab11a was unaffected during zygote to ookinete development ( Fig S3). Activated-Unfertilized 24h WT-GFP Female Gametes (AUFG -treated prior to and during activation with 2-Deoxy-D-glucose, 2DG [22] show expression of PbRAB11A and p25 ( Fig 2B, E) indicating activation of translationally stored mRNAs occurred and was not dependent upon fertilisation ( Fig S3). An imaging flow cytometry (IFC) strategy ( Fig S4, S5) was developed to quantitate the ookinete conversion rate and confirmed the results seen by conventional microscopy ( Fig 2F).…”

“…After 15 minutes, activation centres defined as actively moving clumps of cells were counted using 10X objective on the light microscope (Primo Star-Zeiss). Fertility of mutant gametes was assessed through in-vitro cross fertilization with P. berghei parasites able to produce only male (P47 KO) [39] or female (P48/45 KO) gametes [40], respectively, by inhibiting mutant male gamete exflagellation through 2DG treatment [22].…”

“…To prevent fertilization of female gametes, unactivated gametocytes were cultured in enriched PBS (PBS supplemented with 2mM HEPES, 2mM Glucose, 0.4mM NaHCO3, 0.01% BSA) containing 100 mM 2-Deoxy-D-glucose (Sigma) for 45 minutes [22] and filtered through Plasmodipur filters (EuroProxima), washed with ookinete medium and re-cultured in ookinete medium without 2-Deoxy-D-glucose (2DG) for 24h. Female gametocytes activate but fertilization is prevented due to a blockage in male gamete exflagellation [22].…”

A novel lipoate attachment enzyme is shared by Plasmodium and Chlamydia species

“…These proteins are both components of the tricarboxylic acid (TCA) cycle, raising the possibility that protein lipoylation regulates the activity of this pathway. TCA cycle activity is thought to be critical for parasite survival during different life cycle stages, such as the mosquito stage (Ke et al, 2015;Srivastava et al, 2016), suggesting a critical role for lipoylation during these stages of parasite development. Additionally, lipoylation of BCDH may be important for generating acetyl-CoA for acetylation reactions in other subcellular compartments of the parasite, such as the cytosol and nucleus.…”