Calcium Dependent Protein Kinase 3 is not essential for the asexual replication of Plasmodium falciparum

Calcium dependent protein kinases are essential at various stages of malaria parasite development within the vertebrate host and the mosquitoes. In the rodent malaria parasite, Plasmodium berghei, CDPK3 is essential for the sexual stage development of the parasite within mosquitoes. However, the function of CDPK3 in the most lethal human malaria parasite, P. falciparum remains unexplored. Moreover, the calcium dependent kinase activity of CDPK3 has not been experimentally tested. With the aim to biochemically characterize CDPK3 and perform its functional evaluation in the asexual replication of P. falciparum, here we have expressed the full-length CDPK3 in E. coli and demonstrated that it is a bona fide calcium dependent kinase using a luminescence-based assay and a semi-synthetic epitope approach. Complete knock-out of cdpk3 using CRISPR/Cas9 did not show any defect in the asexual replication of the parasite and the knockout parasites look morphologically similar to the wild type. Our study suggests that cdpk3 is not essential for the asexual replication of the parasite under in vitro culture conditions. Perhaps CDPK3 is required for the sexual development of P. falciparum like its ortholog in the rodent malaria parasite. CDPK3 may be a good target for the development of transmission blocking drugs.