Using photoaffinity labelling to study pantothenamide uptake in malaria parasites

Abstract

Pantothenamides (PanAms) comprise a promising class of antimalarial compounds that kill asexual blood-stage Plasmodium falciparum parasites and block transmission. Intriguingly, the most advanced PanAm in drug development, MMV693183, is approximately 100 times more potent against female gametocytes than males. We hypothesized that this specificity is explained by a difference in PanAm uptake, which we studied using a PanAm-based photoaffinity labelling (PAL) probe. We successfully synthesized a probe that competed with MMV693183 in drug sensitivity assays, while the probe did not display high potency by itself. We observed no significant difference in median fluorophore-labelled probe signal intensity between male and female gametocytes, although there might be a difference in subcellular localization of the probe between the sexes. By combining PAL with affinity purification and mass spectrometry, we were not able to identify novel candidate PanAm transporters. We conclude that PAL provides evidence that differences in PanAm uptake do not underly differences in PanAm sensitivity between the gametocyte sexes.