Malarial molecular chaperones of the Plasmodium falciparum infected erythrocyte

Thesis

Resistance to common antimalarials is growing, resulting in the need to develop new therapeutics with the aim of disease elimination. Here we present the malarial molecular chaperones of the Plasmodium falciparum infected erythrocyte as potential drug targets and provide structural information for structure-based drug design. The parasite exports a single Hsp70 into the erythrocyte, PfHsp70-x, which has been linked to virulence. PfHsp70-x colocalises in J-dots with two parasite Hsp40 proteins – PFA0660w and PFE0055c. PFA0660w is a specific stimulator of PfHsp70-x whilst PFE0055c can also stimulate the activity human chaperones.

In this thesis, it was shown that PfHsp70-x is important in the parasite’s response to heat shock at certain stages of the intraerythrocytic life cycle. The ATPase domain of PfHsp70-x was structurally determined using X-ray crystallography and a unique druggable pocket was discovered. Numerous commercially available Hsp70 inhibitors were found to successfully inhibit the basal and/or the Hsp40 stimulated activity of PfHsp70-x. A combination of X-ray crystallography, biochemical assays and biophysical methods were employed to characterise the interaction of PfHsp70-x with PFA0660w and PFE0055c to understand the specificity of stimulation.

The role of PfHsp70-x in protection and proliferation of the parasite, alongside the inhibition of PfHsp70-x by available Hsp70s inhibitors, demonstrates the possibility of repurposing chaperone inhibitors as antimalarials. Differential interactions of PfHsp70-x with its cochaperones provide a route for specifically targeting PfHsp70- x as Hsp70 proteins require stimulation by a Hsp40. The work presented here characterises just a part of a wider network of chaperones likely formed of parasite proteins and hijacked human chaperones.

Authors: Day, J

• DOI: 10.5287/ora-ppyryb98m
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford