Function of a putative iron transporter in the Plasmodium apicoplast

Human malaria caused by Plasmodium falciparum parasites remains a devastating infectious disease marked by increasing treatment failures with frontline artemisinin combination therapies. Plasmodium parasites have evolved specialized metabolic strategies that enable them to infect and grow within red blood cells. Identifying these adaptations will give insight into Plasmodium evolution and identify new parasite-specific therapeutic targets. Parasites require nutritional iron to support critical metabolic pathways that include DNA synthesis and repair, ribosome assembly, mitochondrial electron transport chain function, and isoprenoid precursor synthesis in the apicoplast organelle. Although it has been known for decades that iron chelators effectively block parasite growth inside red blood cells, the pathways and mechanisms used by parasites to obtain iron for intracellular metabolism remain sparsely defined. Identification of iron transporters has been especially challenging given low sequence similarity between many parasite proteins and well-studied proteins from other organisms, including yeast and mammals.

Basic mechanisms of iron uptake into the apicoplast are currently unknown. In an exciting preliminary advance, we have used an innovative affinity screen to identify a highly divergent parasite protein (Pf3D7_1248300) that is targeted to the apicoplast and shows high structural homology to pentameric metal transporters in bacteria, to which the endosymbiotic apicoplast is evolutionarily related. In proposed studies, we will test our central hypothesis that this protein is essential for parasite viability and required for iron-dependent metabolism in the apicoplast. This hypothesis will be tested in two aims. First, CRISPR/Cas9 will be used to tag the gene encoding this putative transporter to encode an epitope tag and a conditional regulation system that enables ligand- dependent protein expression. These tagged parasites will then be used to test and understand the sub-organellar localization and essentiality of this protein for parasite viability and apicoplast biogenesis. Second aim will test if knockdown of this protein selectively impairs iron-dependent metabolism inside the apicoplast. These studies will unravel a new molecular paradigm for iron mobilization into the apicoplast organelle and unveil a potential new therapeutic target, especially as preliminary results suggest that small molecules can selectively target this protein. These studies will also involve the rigorous training of a talented female PhD student from an underrepresented Native American background and mentorship of a summer undergraduate student through the Utah Genomics Summer Research for Minorities or Native American Research Internship programs.

NIH Project details

Basic Science

May 2024 — Mar 2026

$231,000

United States