Genetic interrogation of putative proteases in Plasmodium falciparum
File(s)
Author(s)
Ridewood, Sophie
Type
Thesis or dissertation
Abstract
Malaria remains a major cause of morbidity and mortality around the world. The emergence and spread of parasites resistant to all frontline antimalarials means that the identification of novel targets is vital for the development of drugs with novel mechanisms of action. The protozoan parasites of the Plasmodium genus cause malaria through the continual infection of and egress from red blood cells (RBCs). Plasmodium spp. encode uncharacterised orthologues to approved protease drug targets, namely HIV-1 protease and DPP4, for the treatment of AIDS and diabetes, respectively. In this project, DiCre-mediated conditional truncation of four putative proteases was performed in the malaria parasite, P. falciparum. Truncation of two of four proteins resulted in growth defects in the asexual blood stages. One putative serine protease, named S9C, was found to be important, but not essential, for intraerythrocytic development. The delay in growth was paired with stunted early parasite morphology and abnormal structure of the parasitophorous vacuole, in which the parasite resides within the RBC. A putative aspartyl protease that is conserved in eukaryotes, DNA-damage inducible protein 1 (Ddi1), is essential in the asexual blood stages, and its loss results in an almost complete block of erythrocyte invasion. We found evidence that Ddi1 was implicated in cellular proteostasis, potentially interacting with proteins involved in protein trafficking, sorting and quality control. We also find a potentially conserved interaction between Ddi1 and a subset of ubiquitinated proteins. For both S9C and Ddi1, a conditional allelic replacement with wildtype and mutant alleles demonstrated the importance of the putative proteolytic activity. The importance of the Ddi1 catalytic activity makes it a novel druggable antimalarial target. Furthermore, studying these putative proteases for the first time has uncovered new aspects of parasite biology in P. falciparum.
Version
Open Access
Date Issued
2019-09
Online Publication Date
2021-07-31T23:01:30Z
2021-10-15T11:00:37Z
Date Awarded
2020-02
Copyright Statement
Creative Commons Attribution-Non Commercial 4.0 International Licence
Advisor
Deu Sandoval, Edgar
Baum, Jacob
Blackman, Michael
Holder, Anthony
Sponsor
Biotechnology and Biological Sciences Research Council (Great Britain)
GlaxoSmithKline
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)