Structural studies of the clustering of PfEMP1 proteins on the surface of Plasmodium falciparum-infected erythrocytes

Lead Research Organisation: University of Oxford
Department Name: Biochemistry

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Technical Summary

Malaria is one of the most deadly diseases affecting humanity, causing around 2 million deaths, and 500 million serious cases each year. The symptoms of the disease occur during the erythrocytic phase of the Plasmodium life cycle, when the parasite divides within infected erythrocytes. During this phase, the parasite causes extensive remodelling of the erythrocyte. Structures called knobs form on the erythrocyte surface and adhesive PfEMP1 proteins are clustered at these knobs. This causes infected erythrocyte to adhere to human tissues or to the microvasculature, protecting the parasite from detection by the spleen and prolonging the infection. This adhesion also causes many of the most severe symptoms of malaria, with adhesive erythrocyte blocking tiny capillaries in the brain during cerebral malaria and binding to the placenta during pregnancy-associated malaria.

The parasite protein KAHRP appears to act as the hub around which the knobs are formed. Important in the correct localisation of KAHRP, and the subsequent formation of knobs, is the interaction between KAHRP and the erythrocyte cytoskeletal protein, spectrin. We have determined the spectrin-binding region of KAHRP and have crystals of the KAHRP binding region of spectrin. We will use structural and biophysical methods to characterise this interaction in stereochemical detail.

The intracellular domains of PfEMP1 proteins (the VARC domains) interact with KAHRP and this is thought to be important in clustering PfEMP1 proteins at knobs. We will use structural and biophysical methods, including protein crystallography and nuclear magnetic resonance (NMR) spectroscopy to investigate this interaction in stereochemical detail. We have shown that different peptides from KAHRP interact with VARC and that in the absence of binding partner, VARC is partially disordered. We will use NMR to study VARC-KAHRP complexes and will determine the structures of ordered complexes between KAHRP binding peptides and VARC subdomains.

Finally we will initiate parasite mutagenesis studies in which we replace the KAHRP gene by genes containing mutant KAHRP lacking regions needed to bind to spectrin or VARC. We will study erythrocytes infected with these parasite strains and use confocal microscopy, electron microscopy and adhesion studies to determine the roles of different interactions in knob formation and function.

These studies will provide detailed structural insight into the formation of knobs and will guide future attempts to develop inhibitors to block knob formation - molecules that will be useful as therapeutics for treatment of the symptoms of severe malaria.

Publications

10 25 50
 
Description Investigator Award
Amount £2,087,360 (GBP)
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2013 
End 09/2020
 
Description CMP Copenhagen 
Organisation Copenhagen University Hospital
Country Denmark 
Sector Hospitals 
PI Contribution We have developed a strong collaboration with our colleagues at the University of Copenhagen, in which we have studied the binding of PfEMP1 proteins from the malaria parasite to endothelial receptors. This work has helped secure an investigator award from the Wellcome Trust and has led to a number of exciting projects.
Collaborator Contribution The collaboration is a close one in which my group to structural and biophysical studies and link these to the parasite and epidemiology work from our collaborators.
Impact doi: 10.1038/nature12216.
Start Year 2008