Developmentally regulated expression of ceramide in Trypanosoma cruzi

Amastigote forms of T. cruzi express the specific Ssp-4 surface antigen which is progressively shed, by the action of an endogenous phosphatidylinositol-phospholipase C, during their development into epimastigotes (Andrews et al., J. Exp. Med., 167 (1988) 300-314). We show now that the lipid moiety of the anchor of Ssp-4 is a ceramide which was metabolically labelled with [3H]palmitic acid. The lipid could be cleaved by PI-PLC digestion in vitro, and was identified by methanolysis and reverse phase thin layer chromatography of the products, as palmitoyldihydrosphingosine. Also, the free biosynthesized lipids were investigated in parasites obtained after 0, 24, 48 and 72 h differentiation of trypomastigotes and further incubated with [3H]palmitic acid for 2 h. A maximum of free ceramide was found in the 24 h point, in accordance with the maximum of amastigote forms. In contrast only traces of free ceramide were found in trypomastigotes. The major ceramide (more than 90%) is palmitoyldihydrosphingosine, which is the same as found in the anchor of Ssp-4. The ceramide could play an important role in the cell biology of the parasite as previously found for mammalian cells.