Overlapping and distinct roles of CDPK family members in the pre-erythrocytic stages of the rodent malaria parasite, Plasmodium berghei

Abstract

Invasion of hepatocytes by Plasmodium sporozoites initiates the pre-erythrocytic step of a malaria infection. Subsequent development of the parasite within hepatocytes and exit from them is essential for starting the disease-causing erythrocytic cycle. Identification of signaling pathways that operate in pre-erythrocytic stages provides insight into a critical step of infection and potential targets for chemoprotection from malaria. We demonstrate that P. berghei homologs of Calcium Dependent Protein Kinase 1 (CDPK1), CDPK4 and CDPK5 play overlapping but distinct roles in sporozoite invasion and parasite egress from hepatocytes. All three kinases are expressed in sporozoites. All three are required for optimal motility of sporozoites and consequently their invasion of hepatocytes. Increased cGMP can compensate for the functional loss of CDPK1 and CDPK5 during sporozoite invasion but cannot overcome loss of CDPK4. CDPK1 and CDPK5 expression is downregulated after sporozoite invasion. CDPK5 reappears in a subset of late stage liver stages and is present in all merosomes. Chemical inhibition of CDPK4 and depletion of CDPK5 in liver stages implicate these kinases in the formation and/or release of merosomes from mature liver stages. Furthermore, depletion of CDPK5 in merosomes significantly delays initiation of the erythrocytic cycle without affecting infectivity of hepatic merozoites. These data suggest that CDPK5 may be required for the rupture of merosomes. Our work provides evidence that sporozoite invasion requires CDPK1 and CDPK5, and suggests that CDPK5 participates in the release of hepatic merozoites.

Plasmodium sporozoites on the move: Switching from cell traversal to productive invasion of hepatocytes

“…CDPK4 conditional knockout mutants display a twofold decrease in productive invasion of HepG2 cells, and CDPK4 chemical inhibition leads to reduced sporozoite motility in P. berghei (Govindasamy et al, 2016). CDPK1 and CDPK5 also contribute to sporozoite gliding motility and host cell invasion, although increased cGMP can compensate for the functional loss of CDPK1 and CDPK5 during sporozoite invasion (Govindasamy & Bhanot, 2020). Disruption of CDPK6 gene in P. berghei caused an increase in sporozoite CT activity and reduced hepatocyte invasion, associated with a defect in CSP cleavage (Coppi et al, 2007).…”

Characterization of Three Calcium-Dependent Protein Kinases of Cryptosporidium parvum

“…Recent studies on in Plasmodium spp. have shown some overlapping functions of various CDPKs, which could have reduced the inhibitory effects of these potential CDPK inhibitors on in vitro parasite growth ( Blackman et al, 2020 ; Ghartey-Kwansah et al, 2020 ).…”

Phosphorylation of myosin A regulatesPlasmodiumsporozoite motility and is essential for efficient malaria transmission

“…In T. gondii , phosphorylation of MyoA is dependent on calcium and the calcium dependent protein kinase TgCDPK3 was identified as a kinase to phosphorylate serines in the N-terminus of MyoA (Tang et al , 2014; Gaji et al , 2015). Calcium is also important for activation of Plasmodium sporozoite motility (Carey et al , 2014) and three CDPKs have been shown to impact sporozoite motility with two influenced by protein kinase G (Govindasamy et al , 2016; Govindasamy & Bhanot, 2020). Our data showing that S19 phosphorylation is important during salivary gland invasion, migration in the skin and liver invasion, suggests that similar signaling pathways play a role at different steps during malaria transmission.…”