Abnormal membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes.

The membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes was analysed by employing phospholipase A2 and Merocyanine 540 as external membrane probes. Both bee venom and pancreatic phospholipases A2 failed to hydrolyse phosphatidylserine in uninfected human red cells isolated from in vitro P. falciparum cultures. However, these enzymes under identical conditions readily degraded this aminophospholipid in P. falciparum-infected erythrocytes. Phosphatidylethanolamine hydrolysis also increased in parasitized cells. The degree to which these aminophospholipids were cleaved by the enzymes in intact infected cells depended on the developmental stage of the intracellular parasite, and was maximum at the schizont stage. This was consistent with the finding that the 'fluid-sensing' fluorescent dye, Merocyanine 540, readily labelled both the schizont and trophozoite-infected cells but not the fresh, uninfected or ring-infected erythrocytes. These results demonstrate that P. falciparum produces stage-dependent changes in the membrane phospholipid organization of its host erythrocyte.