Phosphodiesterase beta controls cAMP signalling during malaria parasite erythrocyte invasion

Cyclic nucleotide signalling is a major regulator of malaria parasite differentiation. Specific phosphodiesterase (PDE) enzymes are known to control cGMP levels in the parasite, but the mechanisms by with cAMP is regulated remain enigmatic. Here we show that P. falciparum PDEbeta translocates via the ER to an apical location and finally to the plasma membrane of merozoites within the segmented schizont. PDEbeta is essential for blood stage replication, with conditional gene disruption causing a profound invasion phenotype and rapid death of those merozoites that are able to invade a host erythrocyte. Importantly we also demonstrate that PDEbeta is able to hydrolyse both cAMP and cGMP. Loss of PDEbeta activity results in significantly elevated levels of cAMP which correlate temporally with the observed reduction in merozoite invasion. Quantitative phosphoproteomic analysis revealed a >2-fold increase in phosphorylation for >250 phosphosites following silencing of PfPDEbeta. These included a highly significant increase in phosphorylation at PKA substrate consensus sequences. Our results suggest that dysregulated phosphorylation of MyoA S19 and AMA1 S610 likely contributes to the PfPDEbeta knockout invasion phenotype, that PKG activity governs cAMP levels and PKA activation prior to merozoite egress, and that PfPDEbeta has an essential function in regulation cAMP levels in early intra-erythrocytic development in P. falciparum.