Structural and functional studies of perforin-like proteins implicated in zoonotic parasitic diseases

Apicomplexans contain a unique family of pore forming proteins named perforin-like proteins (PLPs). These are related to well-known effectors found in the immune system including perforin and the complement system which use pore formation on biological membranes as a means of attacking invading pathogens. Many copies of the pore forming protein must bind to the membrane and interact to form a circular pore shape, after which they rearrange to insert themselves into the membrane and punch out a ring of lipids. Apicomplexans are a family of parasites which must travel through cells during infection to complete their lifecycle. PLPs are secreted by the parasites and modify the host cell membrane in a way that allows the parasite to gain entry to and swim through the cell. However, the mechanisms underlying this activity are not currently understood. This project aims to determine the pore forming activity of PLPs, and understand how they facilitate this novel cell traversal activity using structural, biophysical and computational techniques.

BBSRC priority areas:

This project seeks to understand the molecular mechanisms behind a new family of pore forming proteins, which are of particular interest due to their ability to transition from a soluble monomeric to transmembrane state. Knowledge of these proteins also contributes to our understanding of pathogen biology as they act on cellular membranes to allow whole parasites to enter into and travel through cells.

Pore forming proteins have potential wide-ranging biotechnological applications due to their ability to create a pathway for delivery of molecules through biological membranes, with particular applications in biosensing and biotherapeutics. Their study could help to refine our understanding of the pore forming process, to identify new candidates and methods of application in biotechnology.

In addition to the fundamental biological questions these proteins pose, their study also has practical implications, as the apicomplexan parasites infect a range of mammals. Several members of the apicomplexan phylum are major causes of illness and abortion in livestock. As such, these parasites have a huge impact on the productivity and profit of livestock farming worldwide, as well as affecting pets and wild animals. Study of PLPs has focused on the model apicomplexan organisms Toxoplasma and Plasmodium, however PLPs are found throughout the family and may have similar mechanisms of action. Knockout of PLPs in studies performed so far have led to significant reduction in pathogen virulence, therefore understanding the mechanisms of action of PLPs has the potential to provide new strategies for therapy. My project will focus on determining the basis for membrane attack by a Toxoplasma PLP comparing it to one from Plasmodium vivax and then moving towards a study of PLPs from Babesia and Theileria, Apicomplexans which are significant pathogens of livestock.