Plasmodium falciparum dipeptidyl aminopeptidase 3 activity is important for efficient erythrocyte invasion by the malaria parasite

Parasite egress from infected erythrocytes and invasion of new erythrocytes are essential for the exponential asexual replication of the malaria parasite, and both processes are regulated and mediated by proteases. The putative cysteine protease dipeptidyl aminopeptidase 3 (DPAP3) was previously suggested to be essential for parasite egress, but little is known about its biological function. Here, we demonstrate that DPAP3 has proteolytic activity, but contrary to previously studied DPAPs, removal of its prodomain is not required for activation. Interestingly, P. falciparum DPAP3 localizes to merozoite apical organelles from which it is secreted immediately before egress. Using a conditional knock out approach coupled to complementation studies with wild type or mutant DPAP3, we show that DPAP3 activity is critical for efficient RBC invasion and overall parasite replication, and demonstrate that it does not play a role in parasite egress. Overall, this study establishes DPAP3 as a key regulator of erythrocyte invasion.