PR001286 (Project)

Description:Plasmodium falciparum is the most virulent species of parasites that cause malaria. Among other differences, these parasites have a limited reliance on mitochondrial metabolism during their asexual blood stages when compared to model eukaryotes or other parasite stages. Our study aimed to analyze lines of these parasites where one or more of the keto-acid dehydrogenase enzymes that are localized to the mitochondrion were disrupted to determine the importance of acetyl-CoA generation within this organelle. We utilized a targeted HPLC/MS-based approach to profile metabolite abundances and obtain the fractional incorporation of metabolites that are critical to central carbon metabolism (glucose, glutamine, or acetate) into acetyl-CoA and other landmark metabolites across a 2.5-hour time window. Glucose or glutamine were added at standard culture conditions. Acetate experiments used 5 mM acetate, which was shown to permit growth of synthetic lethal lines. The results of these studies demonstrated that synthetic lethal mutant parasites, which were observed when both mitochondrial keto-acid dehydrogenases (PF3D7_0303700.1 and PF3D7_1320800.1) were disrupted, resulted in the lack of incorporation of heavy glucose into acetyl-CoA. However, lines that lacked the synthetic lethal phenotype also resulted in essentially a complete lack of glucose incorporation into acetyl-CoA as long as the mPDH-like subunits (PF3D7_1312600.1 and PF3D7_0303700.1) were disrupted, which suggests that the a-ketoglutarate dehydrogenase enzyme possesses a small amount of enzymatic activity to rescue this metabolic disruption. Furthermore, acetate supplementation experiments have demonstrated that exogenously supplied acetate circumvents these lethal effects and is not notably incorporated into the TCA cycle, which highlights the ability of the nuclear/cytosolic acetyl-CoA synthetase activity to circumvent mitochondrial metabolism given the presence of excess acetate. These studies are necessary for understanding pharmacology effects of relatively new acetyl-CoA-production disrupting drugs and possible resistance mechanisms that may evolve in the future.