Lipid biosynthesis and its influence on the glycosylphosphatidylinositol pathway in protozoan parasistes. (360G-Wellcome-067441_Z_02_B)

Advances in the understanding of general cell-surface architecture of trypanosomatid parasites, particularly human pathogens like Trypanosoma brucei, Trypanosoma cruzi and Leishmania has come about by the identification and structural characterisation of the most abundant cell-surface molecules. The majority of these are glycosylphosphatidylinositol (GPI) anchored glycoproteins and/or GPI-related molecules. Significant differences between the GPI biosynthetic pathways of protozoa and humans has lead to the suggestion that it might be a viable therapeutic target. In T. brucei, the causative agent of African Sleeping Sickness, this has been validated by the lethal disruption of the GPI biosynthetic pathway in the bloodstream form of the parasite by knocking out the TbGPI10 gene. Thus, it follows that the formation of the acceptor and donors required for GPI biosynthesis must also be essential. These incude the biosynthesis pathways of phosphatidylinositol (PI) acceptor, phosphatidylethanolamine (PE) and dolichol-phosphate-mannose (Dol-P-Man) donors. In yeast, several null and conditional (temperature sensitive) mutants of the genes involved in these lipid biosynthetic pathways have been created. These have been invaluable in studying lipid biosynthesis and several of these have been shown to affect GPI biosynthesis. Current knowledge of the biology and biochemistry of these biosynthetic enzymes in trypanosomatids is inadequate in many respects, but advances in molecular and biochemical techniques and the advances in the T. brucei genome project has made available exiting new possibilities for investigations of these biosynthetic enzymes and pathways. Thus, the primary theme of this proposal is to study the enzymology, mechanisms, structure, protein-protein interaction and influence that these biosynthetic enzymes have on the the GPI pathway. Unique pathways and/or enzymes involved in lipid biosynthesis in trypanosomatids may be identified, highlighting potential exploitable differences between mammalian and parasite lipid biosynthesis and providing novel therapeutic targets. Finally, part of the project is to capitalise on pre-existing inhibitors of general lipid biosynthesis having anti-protozoan activity and ascertain whether these inhibitors can be modified so that they can permeate the cell-membrane of living trypanosomes. The proposed project will continue my research interests in GPI biosynthesis, but from a wider perspective, using a multi-disciplinary approach to study parasite lipid biosynthesis and its direct effect on the essential GPI pathway.