Identification and Characterization of Protein-Protein Interaction Effectors Targeting the Invasion Machinery of the Malaria Parasite

Abstract

Emerging resistance of Plasmodium falciparum to current treatments is concerning and requires the development of a new generation of drugs. In pursuit of novel compounds, we have targeted protein-protein interactions (PPIs) essential to the parasite. Plasmodium uses an actomyosin motor, part of the glideosome complex, for gliding and invasion of host cells. A key interaction of the glideosome is between aldolase and the cytoplasmic tail of the thrombospondin-related adhesive protein, TRAP. It is thought that the dynamic aldolase-TRAP complex must dissociate for forward motility and invasion to progress; therefore, we have developed an assay to identify compounds that promote this interaction, resulting in stalled gliding and invasion. We produced MBP-tagged and biotinylated peptides for studying the interaction between aldolase and TRAP using surface plasmon resonance. We have screened the Medicines for Malaria Ventures library and have identified several compounds with concentration-dependent effects in vitro. Five promising compounds were moved forward into parasite gliding and invasion assays. We have observed phenotypic differences in the ability of Plasmodium parasites to glide, and found a reduced gliding velocity and abnormal rates of sporozoite attachment and detachment. To determine the effect on invasion, both red blood cell and hepatocyte invasion assays have been performed. We are currently attempting to determine a co-crystal structure of the ternary aldolase-TRAP-compound complex, and to move promising compounds into an in vivo mouse model.