University of Cambridge
Analysing the role of Protein Disulphide Isomerase in Plasmodium and targeting function to block transmission
Abstract
dc:description.abstractProtein Disulphide Isomerase (PDI)-Trans has been identified as a putative target for transmission blocking interventions in Plasmodium spp. Located on the surface of the male gamete and ookinete, previous studies have demonstrated that this protein is essential for successful malaria transmission. PDIs are chiefly implicated in changing the conformation of other proteins through their influence on disulphide bridges between protein cysteine residues. Though they are classically located in the endoplasmic reticulum, a small population are found on cell surfaces. In humans, surface-PDI dysregulation is the cause of several diseases; as such, multiple clinical and pre-clinical human PDI-inhibitors have been developed for uses against a wide range of diseases. The role of PDI-Trans, and other PDIs, in Plasmodium, is as yet unexamined and uncharacterised. The work undertaken in this thesis identified human PDI-inhibitors used in clinical and pre-clinical studies and demonstrated that they were able to successfully and significantly block Plasmodium berghei transmission, with initial studies translating these promising results to human malaria performed. A medium throughput assay was also identified as predictive for a compound’s efficacy in the low throughput and time consuming ‘gold-standard’ transmission blocking assay, the Standard Membrane Feeding Assay. Investigations were also performed to investigate PDI-Trans’ feasibility as a vaccine target, with mice immunised with recombinant PDI-Trans found to have significantly fewer parasites than non-immunised controls. Despite PDI-Trans’ importance in parasite transmission, little is known about its function or molecular interactions during the transmission stages. Through the use of a series of PDI-Trans-GFP pulldowns, a list of proteins that potentially interact with PDI-Trans pre- and post-activation was generated, with a shortlist of 14 proteins identified through a manual ‘triage’ based on features deemed to be of potential biological importance. PDI-Trans specificity was further investigated through complementation of the ∆PDI-Trans line with extracellular PDI. Human PDI complemented PDI-Trans recovered a limited but significant fertilisation phenotype, both confirming that extracellular PDI activity is essential to transmission and also that a portion of PDI-Trans’ activity might be mutually redundant with other PDIs. Finally, six other PDI-like proteins in the P. berghei genome were investigated. Recombinant regions of the active thioredoxin domains of four of the proteins were generated, and the PDI activity of PDI5 was confirmed for the first time. These findings confirm that PDI-Trans is a promising target for transmission blocking interventions, and that its characterisation and further investigation is both timely and logical.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2024
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Ford, Amelia
- Advisor dc:contributor.advisor
-
- Blagborough, Andrew
Subjects
dc:subject × 4Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.115823
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/379852