Erythrocyte signalling is critical for Plasmodium falciparum invasion

Abstract

AbstractSuccessful Plasmodium falciparum merozoite invasion requires the activation of red blood cell (RBC) signalling pathways. The binding of parasite ligand reticulocyte binding protein homologue 5 (RH5) to its host receptor Basigin is essential for merozoite invasion and triggers a Ca2+ influx in RBCs. Here we observed that RH5-bound RBCs form a multimeric protein complex containing Basigin, CD44 and β2-adrenergic receptor (β2AR), suggesting that RH5-Basigin interaction is functionally associated with the host cAMP signalling pathway. Interestingly, we detected a characteristic rise in cAMP levels in the RBC upon RH5-Basigin interaction, which can be blocked by G protein and cAMP-synthesising adenylyl cyclase (AC) inhibitors. Furthermore, we demonstrated that RBC L-type Ca2+ channel inhibitor and cAMP signalling inhibitors are able to block merozoite invasion. Checkerboard invasion inhibition assay containing different combinations of signalling inhibitors also exhibited a drastic amplification of inhibition levels, indicating that these signalling proteins are functioning in a common signalling cascade to activate the L-type Ca2+ channels. Taken together, this study provides new insights into the role of a host cAMP-Ca2+ signalling pathway during merozoite invasion and sheds new light on antimalarial therapeutic strategies to tackle the high infection rate and growing threat of drug resistant parasites.Key PointsA pre-existing Basigin-associated membrane protein complex undergoes increased protein assembly upon RH5 binding on the RBC surface.Plasmodium falciparum merozoite exploits host cAMP signalling to initiate Ca2+ influx in the RBC.