TgPL2, a patatin-like phospholipase domain-containing protein, is involved in the maintenance of apicoplast lipids homeostasis in Toxoplasma

Patatin-like phospholipases are involved in numerous cellular functions, including lipid metabolism and membranes remodeling. The patatin-like catalytic domain, whose phospholipase activity relies on a serine-aspartate dyad and an anion binding box, is widely spread among prokaryotes and eukaryotes. We describe TgPL2, a novel patatin-like phospholipase domain-containing protein from the parasitic protist Toxoplasma gondii. TgPL2 is a large protein, in which the key motifs for enzymatic activity are conserved in the patatin- like domain. Using immunofluorescence assays and immunoelectron microscopy analysis, we have shown that TgPL2 localizes to the apicoplast, a non-photosynthetic plastid found in most apicomplexan parasites. This plastid hosts several important biosynthetic pathways, which makes it an attractive organelle for identifying new potential drug targets. We thus addressed TgPL2 function by generating a conditional knockdown mutant and demonstrated it has an essential contribution for maintaining the integrity of the plastid. In absence of TgPL2, the organelle is rapidly lost and remaining apicoplasts appear enlarged, with an abnormal accumulation of membranous structures, suggesting a defect in lipids homeostasis. More precisely, analyses of lipid content upon TgPL2 depletion suggest this protein is important for maintaining levels of apicoplast-generated fatty acids, and also regulating phosphatidylcholine and lysophosphatidylcholine levels in the parasite.