Extracellular ATP triggers proteolysis and cytosolic Ca2+ rise in Plasmodium berghei and Plasmodium yoelii malaria parasites

Abstract

BackgroundPlasmodium has a complex cell biology and it is essential to dissect the cell-signalling pathways underlying its survival within the host.MethodsUsing the fluorescence resonance energy transfer (FRET) peptide substrate Abz-AIKFFARQ-EDDnp and Fluo4/AM, the effects of extracellular ATP on triggering proteolysis and Ca2+ signalling in Plasmodium berghei and Plasmodium yoelii malaria parasites were investigated.ResultsThe protease activity was blocked in the presence of the purinergic receptor blockers suramin (50 μM) and PPADS (50 μM) or the extracellular and intracellular calcium chelators EGTA (5 mM) and BAPTA/AM (25, 100, 200 and 500 μM), respectively for P. yoelii and P. berghei. Addition of ATP (50, 70, 200 and 250 μM) to isolated parasites previously loaded with Fluo4/AM in a Ca2+-containing medium led to an increase in cytosolic calcium. This rise was blocked by pre-incubating the parasites with either purinergic antagonists PPADS (50 μM), TNP-ATP (50 μM) or the purinergic blockers KN-62 (10 μM) and Ip5I (10 μM). Incubating P. berghei infected cells with KN-62 (200 μM) resulted in a changed profile of merozoite surface protein 1 (MSP1) processing as revealed by western blot assays. Moreover incubating P. berghei for 17 h with KN-62 (10 μM) led to an increase in rings forms (82% ± 4, n = 11) and a decrease in trophozoite forms (18% ± 4, n = 11).ConclusionsThe data clearly show that purinergic signalling modulates P. berghei protease(s) activity and that MSP1 is one target in this pathway.

Cytoplasmic free Ca2+ is essential for multiple steps in malaria parasite egress from infected erythrocytes

“…Probenecid-containing medium was used for these experiments to prevent dye extrusion from parasites [40]. In some recordings a gradual increase in the Fluo-4 fluorescence signal that precedes the fluorescence transients due to erythrocyte membrane poration was observed (see example in Figure 1B; note that the gradual fluorescence increase coincides with the beginning of the host cell shape transformation).…”

Propensity of red blood cells to undergo P2X7 receptor–mediated phosphatidylserine exposure does not alter during in vivo or ex vivo aging

“…10,32--34 Additionally, P2X7 activation is deemed to allow malarial parasites to invade or escape RBCs. 47,48 Thus, given the presence of functional P2X7 on stored RBCs, RBC concentrates may provide a readily available source to further elucidate the physiological and pathophysiological roles of P2X7 in human RBCs.…”

Kinetic and biochemical characterization of Trypanosoma evansi nucleoside triphosphate diphosphohydrolase

“…Therefore, it is possible that T. evansi NTPDase is involved in parasite purinergic signaling by modulating extracellular ATP levels. Indeed, ATP is shown to be involved in purinergic signaling and host infection in malaria parasites (Cruz et al, 2012;Levano-Garcia et al, 2010;Ramdani and Langsley, 2014).…”