Functional characterization of malaria parasites deficient in the K⁺ channel Kch2

K⁺ channels are integral membrane proteins, which contribute to maintain vital parameters such as the cellular membrane potential and cell volume. Malaria parasites encode two K⁺ channel homologues, Kch1 and Kch2, which are well-conserved among members of the Plasmodium genus. In the rodent malaria parasite P. berghei, the functional significance of K⁺ channel homologue PbKch2 was studied using targeted gene knock-out. The knockout parasites were characterized in a mouse model in terms of growth-kinetics and infectivity in the mosquito vector. Furthermore, using a tracer-uptake technique with ⁸⁶Rb⁺ as a K⁺ congener, the K⁺ transporting properties of the knockout parasites were assessed.

Genetic disruption of Kch2 did not grossly affect the phenotype in terms of asexual replication and pathogenicity in a mouse model. In contrast to Kch1-null parasites, Kch2-null parasites were fully capable of forming oocysts in female Anopheles stephensi mosquitoes. ⁸⁶Rb⁺ uptake in Kch2-deficient blood-stage P. berghei parasites (Kch2-null) did not differ from that of wild-type (WT) parasites. About two-thirds of the ⁸⁶Rb⁺ uptake in WT and in Kch2-null parasites could be inhibited by K⁺ channel blockers and could be inferred to the presence of functional Kch1 in Kch2 knockout parasites. Kch2 is therefore not required for transport of K⁺ in P. berghei and is not essential to mosquito-stage sporogonic development of the parasite.