Role of calcium and erythrocyte cytoskeleton phosphorylation in the invasion of Plasmodium falciparum.

The role of calcium in the invasion of the human erythrocyte by the parasite Plasmodium falciparum was studied. The intraerythrocytic and intraparasitic concentrations of Ca2+ were modified using calcium-ionophore A23187 and the chelator EGTA. The Ca2+ inside the parasite appeared to be necessary for the normal completion of invasion. We determined that in recently invaded erythrocytes (2 h), the Ca2+ concentration increased about 10 times. Merozoite invasion produced a decrease in beta-spectrin phosphorylation and an increase in the phosphorylation of a protein with band 4.1 mobility. These changes were similar to those produced by an ionophore-mediated Ca2+ influx in uninfected erythrocytes. These facts support the idea that a calcium influx into erythrocytes might precede or accompany merozoite invasion, triggering a series of molecular events, including phosphorylation and dephosphorylation of cystoskeletal proteins.