A bacterial-type cardiolipin synthase in Plasmodium spp. supports mitochondrial respiration and is important for liver stage maturation

The mitochondrion of malaria-causing Plasmodium spp. supports parasite energy requirements, pyrimidine and ubiquinone biosynthesis and [Fe-S] formation. As parasites transition from the host liver to asexual and sexual blood stages, metabolic shifts of ATP generation through glycolysis or mitochondrial oxidative phosphorylation are accompanied by change in mitochondrial number, branching complexity and development of cristae. The final step of synthesis of cardiolipin (CL), a critical phospholipid for mitochondrial biogenesis and function, is catalyzed by cardiolipin synthase (Cls). Plasmodium spp. carry an uncharacterized, putative bacterial-type Cls distinct from Cls of mammalian hosts. We probed enzyme activity of the phospholipase D-type recombinant Plasmodium falciparum Cls. Antibodies generated against PfCls localized it to the mitochondrion in asexual blood stages; additional PfCls signal was observed in the cytosolic periphery in late-gametocytes, accompanied by CL staining in the parasite plasma membrane. To investigate the impact of Cls on parasite life cycle progression, we generated its knockout in the rodent parasite P. berghei. PbCls KO parasites had significantly impaired asexual blood-stage proliferation associated with lower abundance of CL molecular species. They showed a marked reduction in mitochondrial membrane potential and basal oxygen consumption rate. While PbCls-deficient parasites completed development within the mosquito and generated sporozoites capable of hepatocyte invasion, they exhibited a severe defect in liver-stage maturation. Plasmodium Cls is thus a vital component of malaria parasite development with a critical role in maintaining mitochondrial function.