Glycosylphosphatidylinositols of apicomplexan parasites: a structure-activity relationship analysis
Résumé
Glycosylphosphatidylinositols (GPIs) are widespread among eukaryotes, and the expression of GPI-anchored proteins and free GPIs is particularly abundant among the parasitic protozoa. The basic structure of GPIs consists of ethanolamine, mannose, non-acetylated glucosamine, inositol and a lipid-moiety, in part linked by diphosphate bridges. In addition, the evolutionary conserved core structure undergoes species-specific structural variations. The synthesis of GPI anchors takes place in the endoplasmic reticulum and requires many different steps. Protocols used for the identification and characterization of GPIs depend mainly upon sufficient amounts of material or metabolic labelling techniques using radioactive GPI precursor molecules, organic solvent extraction procedures, the use of specific enzymes an of thin-layer chromatography analysis. Responses of host cells to GPIs of apicomplexan parasites (Babesia divergens, Plasmodium falciparum, Neospora caninum, Toxoplasma gondii) have been studied and a structure-activity relationship can be outlined on cytokine production (1-3), Toll-like receptor activation (2-4) and apoptosis (5-6).