Functional analysis of the "Apical Membrane Antigen 1": Investigating the role of phosphorylation of the blood-stage vaccine candidate in the malaria parasite Plasmodium falciparum

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A key process in the lifecycle of the malaria parasite Plasmodium falciparum is the invasion of human erythrocytes. Entry into the host cell requires the apical membrane antigen 1 (AMA-1), a type I transmembrane protein located in the micronemes of the merozoite. Although AMA-1 is evolving into the leading blood-stage malaria vaccine candidate, its precise role in invasion is still unclear. Mutational analysis of the cytoplasmic domain of AMA-1 suggested an important role for the phosphorylation to mediate host cell invasion. It is proposed to validate in depth this phosphorylation of type I transmembrane proteins as one key step in the invasion process of erythocytes. Firstly, the precise timing of AMA-1 phosphorylation and its functional consequences will be elucidated. Secondly, PfPKA, a kinase known to be capable to phosphorylate recombinant AMA-1, will be validated in vivo and in vitro as a putative drug target using a kinase specific inhibitory library. Additional kinases involved in the phosphorylation event will be attempted to identify. Finally, the putative phosphorylation of other type 1 transmembrane proteins known to be involved in invasion (like DBL, RH and the TRAP family) will be analyzed and the functional consequences investigated. Targeting the responsible kinase(s) provide an attractive target for novel therapeutic drug strategies independent of an antibody based approach that is hampered by antigenic escape regions in polymorphic extracellular domains of adhesins in the malaria parasite.