Inhibition of protein N-myristoylation blocksPlasmodium falciparumintraerythrocytic development, egress, and invasion

Abstract

We have combined chemical biology and genetic modification approaches to investigate the importance of protein myristoylation in the human malaria parasite, Plasmodium falciparum. Parasite treatment during schizogony in the last ten to fifteen hours of the erythrocytic cycle with IMP-1002, an inhibitor of N-myristoyl transferase (NMT), led to a significant blockade in parasite egress from the infected erythrocyte. Two rhoptry proteins were mislocalized in the cell, suggesting that rhoptry function is disrupted. We identified sixteen NMT substrates for which myristoylation was significantly reduced by NMT inhibitor treatment, and of these, six proteins were substantially reduced in abundance. In a viability screen, we showed that for four of these proteins replacement of the N-terminal glycine with alanine to prevent myristoylation had a substantial effect on parasite fitness. In detailed studies of one NMT substrate, glideosome associated protein 45 (GAP45), loss of myristoylation had no impact on protein location or glideosome assembly, in contrast to the disruption caused by GAP45 gene deletion, but GAP45 myristoylation was essential for erythrocyte invasion. Therefore, there are at least three mechanisms by which inhibition of NMT can disrupt parasite development and growth: early in parasite development, leading to the inhibition of schizogony and formation of ‘pseudoschizonts’, which has been described previously; at the end of schizogony, with disruption of rhoptry formation, merozoite development and egress from the infected erythrocyte; and at invasion, when impairment of motor complex function prevents invasion of new erythrocytes. These results underline the importance of P. falciparum NMT as a drug target because of the pleiotropic effect of its inhibition.

Identification of potent and selectiveN-myristoyltransferase inhibitors ofPlasmodium vivaxliver stage hypnozoites and schizonts

“…The enzyme NMT is expressed throughout the Plasmodium life cycle and is a promising target for antimalarial drug development. Schlott et al (2021) showed that NMT inhibition disrupts at least 3 vital pathways of the parasite lifecycle: early schizont development, merozoite formation, and merozoite egress (15). Despite this promise, the enzyme has been deprioritized as an antimalarial target due to challenges in identifying parasite-selective inhibitors and a slow mechanism of action (16).…”

“…also report high-affinity compounds that kill blood- and liver stage parasites; Pf NMT with an IC 50 value of 8 nM, up to fourfold selectivity over Hs NMT1/2, P. falciparum blood stage EC 50 value of 302 nM, and P. berghei liver stage EC 50 value of 372 nM ( 14 ). Pharmacological inhibition of NMT prevents the completion of blood-stage development of P. falciparum partly owing to the inhibition of the inner membrane complex formation ( 15 ). Thus, selective targeting of NMT could aid in the development of a drug that targets multiple life cycle stages.…”

Plasmodium sporozoite disintegration during skin passage limits malaria parasite transmission

“…Lastly, as malaria parasites can be targeted within mosquitoes, e.g., through mosquito uptake of antiparasitic drugs (Paton et al , 2019), it might be feasible to target the parasite cell shape maintenance pathways with small molecules within the insect to prevent the transmission of the parasite. While concavin might not directly be targetable, enzymes involved in overall cell shape maintenance such as palmitoyl transferases (Wang et al , 2005; Santos et al , 2015; Hopp et al , 2021; Schlott et al , 2021) could be good candidate targets.…”

Marine gregarine genomes reveal the breadth of apicomplexan diversity and provide new insights on gliding motility

“…GAP45 is thought to maintain the interaction between the IMC and the plasma membrane, and acts as an essential bridge between the two structures 102 . Deleting GAP45 has been proved to prevent glideosome assembly in P. falciparum 103 . Perhaps the absence of GAP45 in gregarines and Cryptosporidium could be compensated by other GAP-like proteins or it may not even be necessary.…”