Purinergic signalling is involved in the malaria parasite Plasmodium falciparum invasion to red blood cells

Plasmodium falciparum, the most important etiological agent of human malaria, is endowed with a highly complex cell cycle that is essential for its successful replication within the host. A number of evidence suggest that changes in parasite Ca2+ levels occur during the intracellular cycle of the parasites and play a role in modulating its functions within the RBC. However, the molecular identification of Plasmodium receptors linked with calcium signalling and the causal relationship between Ca2+ increases and parasite functions are still largely mysterious. We here describe that increases in P. falciparum Ca2+ levels, induced by extracellular ATP, modulate parasite invasion. In particular, we show that addition of ATP leads to an increase of cytosolic Ca2+ in trophozoites and segmented schizonts. Addition of the compounds KN62 and Ip5I on parasites blocked the ATP-induced rise in [Ca2+](c). Besides, the compounds or hydrolysis of ATP with apyrase added in culture drastically reduce RBC infection by parasites, suggesting strongly a role of extracellular ATP during RBC invasion. The use of purinoceptor antagonists Ip5I and KN62 in this study suggests the presence of putative purinoceptor in P. falciparum. In conclusion, we have demonstrated that increases in [Ca2+](c) in the malarial parasite P. falciparum by ATP leads to the modulation of its invasion of red blood cells.