Phospholipid composition, cholesterol content and cholesterol exchange in Plasmodium falciparum-infected red cells.

The membrane lipid composition and [3H]cholesterol exchange rate were studied in both normal human erythrocytes and those infected with the human malaria Plasmodium falciparum. The host cell membrane was separated from parasite membranes using the Affigel (731) bead method. The purity of the membrane preparation was very high, as judged by SDS-PAGE, and in several instances was estimated to be greater than 98% as determined by the activity of the parasite membrane-specific enzyme, choline phosphotransferase. No difference was found in the content of phosphatidylethanolamine and only small changes were observed for phosphatidylcholine and phosphatidylserine. The sphingomyelin content in red cell membranes of both trophozoite- and schizont-infected cells was up to 47% less than that of uninfected cells, and the cholesterol/phospholipid ratio was decreased 55%. Trophozoite- and schizont-infected cells exchanged 29 and 33% less cholesterol, respectively, than uninfected cells. These changes in lipid composition and cholesterol exchange could have a marked effect on the function of the red cell membrane of malaria-infected cells and may be responsible, in part, for the increased fluidity and permeability of P. falciparum-infected erythrocytes.