Mitochondrial ATP synthase is dispensable in blood-stage Plasmodium berghei rodent malaria but essential in the mosquito phase

Abstract

Mitochondrial ATP synthase is driven by chemiosmotic oxidation of pyruvate derived from glycolysis. Blood-stage malaria parasites eschew chemiosmosis, instead relying almost solely on glycolysis for their ATP generation, which begs the question of whether mitochondrial ATP synthase is necessary during the blood stage of the parasite life cycle. We knocked out the mitochondrial ATP synthase β subunit gene in the rodent malaria parasite, Plasmodium berghei, ablating the protein that converts ADP to ATP. Disruption of the β subunit gene of the ATP synthase only marginally reduced asexual blood-stage parasite growth but completely blocked mouse-to-mouse transmission via Anopheles stephensi mosquitoes. Parasites lacking the β subunit gene of the ATP synthase generated viable gametes that fuse and form ookinetes but cannot progress beyond this stage. Ookinetes lacking the β subunit gene of the ATP synthase had normal motility but were not viable in the mosquito midgut and never made oocysts or sporozoites, thereby abrogating transmission to naive mice via mosquito bite. We crossed the self-infertile ATP synthase β subunit knockout parasites with a male-deficient, self-infertile strain of P. berghei, which restored fertility and production of oocysts and sporozoites, which demonstrates that mitochondrial ATP synthase is essential for ongoing viability through the female, mitochondrion-carrying line of sexual reproduction in P. berghei malaria. Perturbation of ATP synthase completely blocks transmission to the mosquito vector and could potentially be targeted for disease control. malaria | ATP synthase | ookinetes | mitochondrial endosymbiosis | aerobic respiration

Apicomplexan Energy Metabolism: Carbon Source Promiscuity and the Quiescence Hyperbole

“…), Plasmodium (in erythrocytic stages) has opted for fast generation of ATP through substrate-level phosphorylation and secretion of lactate as an end-product (aerobic fermentative glycolysis), as opposed to the 'slow but efficient' mitochondrial oxidative phosphorylation and complete oxidation [29]. Reasons for this dependence on glycolytic fermentation remain unclear -after all, blood stages of Plasmodium certainly have access to oxygen -but it may be a way of avoiding excessive reactive oxygen species (ROS) production in an environment already under considerable stress due to hemoglobin breakdown [30,31]. In any case, reliance on glycolysis led to the assumption that mitochondria might be substantially obsolete in blood-stage parasites.…”

“…This includes differentiation of gametes into ookinetes, invasion of the mid-gut epithelium, oocyst formation, and, ultimately, differentiation into sporozoites [77,78]. The increased reliance on the TCA is supported by upregulation of TCA enzymes in gametocyte stages [79,80] and the profound physiological consequences of genetic disruption and/or chemical inhibition of these enzymes (Figure 1) [26,31,36,43,44,46,51,62,81].…”

“…Deletion of KDH in the insect-transmissible NF54 strain of P. falciparum [36], and SDH [43], NDH [44], ATP synthase [31], or BCKDH [46] in P. berghei, all result in failure of normal post-fertilization progression to ookinetes and/or oocysts, although viable gametes are apparently formed. A similar phenotype is observed in P. berghei PEP carboxylase mutants [51].…”

“…do require mitochondrial metabolism because they are susceptible to drugs targeting the ETC, such as atovaquone[ 1 2 _ T D $ D I F F ] , that inhibits complex III [32][33][34][35][36][37]. Evidently this is not for ATP synthesis because inhibition of the ETC has little effect on cellular ATP levels [38][39][40], and deletion of the functional b-subunit of ATP synthase can be tolerated in blood stages of P. berghei [31]. Heme biosynthesis, which is reliant on TCA-derived succinyl-CoA, is dispensable in asexual blood stages [41,42], and thus dissipation of reducing power from TCA activity for this pathway is not required.…”

Distinct Prominent Roles for Enzymes of Plasmodium berghei Heme Biosynthesis in Sporozoite and Liver Stage Maturation

“…Interestingly, the antimalarial activity of atovaquone-proguanil strictly depends on arrest of the pyrimidine biosynthesis pathway by indirect inhibition of Plasmodium dihydroorotate dehydrogenase, which relies on the ETC to recycle electrons (17,22). On the other hand, the respiratory activity of the Plasmodium ETC is essential during parasite development in the Anopheles vector, as shown by normal blood stage growth and complete arrest of oocyst development in Plasmodium berghei mutants that contain targeted deletions of type II NADH:ubiquinone dehydrogenase or the ATP synthase ␤ subunit (23,24).…”