Changes in Trypanosoma cruzi phospholipid turnover induced by parasite contact with cell membranes

To investigate the possibility that cell contact could initiate a series of signals in both the host cell and the flagellate protozoan Trypanosoma cru zi, we studied [P-32]-phospholipid turnover during parasite interaction wit h cellular membranes in vitro. Lipid alterations were produced in the paras ite during the initial period of contact with the plasma membranes of human erythrocytes. In the presence of calcium an increment in phosphalidylethan olamine was observed with a concomitant decrease in phosphatidic acid fract ions, whereas these modifications were not observed in the absence of calci um. There was an evident decrease in phosphatidylcholine and a shift in the phosphatidylinositol/lysophosphatidylethanolamine fraction among the phosp holipids of major turnover in the absence or presence of calcium. Among the minor labeled species, lysophosphatidylcholine reached levels that duplica ted control values, whereas the amounts of lysophosphatidylinositol, phosph atidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate dimin ished by over 50%. All of these variations indicate that the parasite's con tact with plasma membranes induces changes involving T. cruzi phospholipids and suggest the participation of these compounds in the activation of intr acellular mechanisms that might be important during the life cycle of this parasite.