Abstract
Toxoplasma gondii is a unicellular parasite characterized by a unique extracellular and intracellular membrane compartments. Lipid composition of subcellular membranes has not been determined, limiting our understanding of lipid homeostasis, control and trafficking, a series of processes involved in pathogenesis. In addition to a mitochondrion, Toxoplasma contains a plastid called the apicoplast. Occurrence of a plastid raised the question of the presence of chloroplast galactolipids. Using three independent rabbit and rat antibodies against digalactosyldiacylglycerol (DGDG) from plant chloroplasts, we detected a class of Toxoplasma lipids harboring a digalactolipid-like epitope (DGLE), Immunolabelling characterization supports that DGLE polar head is similar to that of DGDG. Mass spectrometry analyses pointed dihexosyl-lipids having various hydrophobic moieties (ceramide, diacylglycerol, acylalkylglycerol), that might react with anti-DGDG, but we cannot exclude that more complex dihexosyl-terminated lipids might also be immunolabelled. DGLE localization was analyzed by immunofluorescent and immunoelectron microscopy and confirmed by subcellular fractionation. No immunolabeling of the apicoplast could be observed. DGLE is scattered in pellicle membrane domains in extracellular tachyzoites and is relocalized to the anterior tip of the cell upon invasion, in an actin-dependent manner, providing insights on a possible role in pathogenetic process. DGLE was detected in other Apicomplexa, i.e. Neospora, Plasmodium, Babesia and Cryptosporidium.