Medical Biology - Theses
Permanent URI for this collection
Search Results
1 - 1 of 1
-
ItemCharacterization of plasmepsin X as a cross-species antimalarial target( 2019)The emergence and spread of drug resistance have hindered the campaign for malaria eradication. The development of new drug targets is critical for our anti-malarial arsenal of interventions. Plasmepsins, which are aspartic proteases expressed by malaria parasites, serve important functions for parasite survival. Among the 10 members of this enzyme family, plasmepsin X (PMX) is essential for P. falciparum growth and has been shown to be involved in the egress of merozoites from infected red blood cells and the invasion of merozoites into red blood cells. Several aspartic protease inhibitors have anti-malarial activity on P. falciparum and are proposed to target PfPMX. The aim of this project was to investigate if these compounds affect P. knowlesi growth and whether PMX is a cross-species target for antimalarial development. This work showed that two aspartic protease inhibitors, 49c and 1SR, caused inhibition of P. knowlesi parasite growth. In further studies, live cell imaging demonstrated that these compounds inhibit P. knowlesi parasite growth by blocking parasite egress. Next, the optimal condition for protease activity was characterised after the expression and purification of a functional recombinant P. knowlesi plasmepsin X (rPkPMX). Using a fluorogenic protease assay, both 49c and 1SR were shown to inhibit the activity of rPkPMX. Furthermore, rPkPMX was able to cleave synthetic substrates, which were based on the predicted cleavage sites of PfSUB1, PfRAP1, PfRh2, TgROP1 and TgMIC6 predicted cleavage sites. By screening a panel of aspartic protease inhibitors, the BACE1 inhibitor, LY2886721, was identified as an inhibitor of rPkPMX activity as well as P. knowlesi and P. falciparum parasite growth. Therefore, PMX can be used as a cross-species target for antimalarial drug development.