Gene expression signatures and small-molecule compounds link a protein kinase to Plasmodium falciparum motility

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Calcium-dependent protein kinases play a crucial role in intracellular calcium signaling in plants, some algae and protozoa. In Plasmodium falciparum, calcium-dependent protein kinase 1 (PfCDPK1) is expressed during schizogony in the erythrocytic stage as well as in the sporozoite stage. It is coexpressed with genes that encode the parasite motor complex, a cellular component required for parasite invasion of host cells, parasite motility and potentially cytokinesis. A targeted gene-disruption approach demonstrated that pfcdpk1 seems to be essential for parasite viability. An in vitro biochemical screen using recombinant PfCDPK1 against a library of 20,000 compounds resulted in the identification of a series of structurally related 2,6,9-trisubstituted purines. Compound treatment caused sudden developmental arrest at the late schizont stage in P. falciparum and a large reduction in intracellular parasites in Toxoplasma gondii, which suggests a possible role for PfCDPK1 in regulation of parasite motility during egress and invasion.

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Figure 1: pfcdpk1 is coexpressed with genes involved in parasite motility.
Figure 2: Comparative genome hybridization for knockout strains.
Figure 3: Effect of purfalcamine on parasitemia.
Figure 4: Representative images from a T. gondii invasion assay carried out in the presence of varying concentrations of purfalcamine.
Figure 5: Structure-based ligand docking analysis.


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We thank V. Nussenzweig (New York University) for providing oocyst and sporozoite stages of P. yoelii and A. Godfrey-Certner for her assistance with the T. gondii invasion assays. This work was supported by a grant to E.A.W. from the Ellison Foundation, the Keck Foundation and the US National Institutes of Health (AI059472-02), a grant to G.E.W. from the US National Institutes of Health (AI054961), and grants to the Genomics Institute of the Novartis Research Foundation from the Wellcome Trust and the Medicines for Malaria Venture.

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Correspondence to Elizabeth A Winzeler.

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