Motor Complex of Plasmodium falciparum: PHOSPHORYLATION BY A CALCIUM-DEPENDENT PROTEIN KINASE

• Published in: The Journal of biological chemistry 2008-11, Vol.283 (45), p.30980-30989
• Main Authors: Green, Judith L, Rees-Channer, Roxanne R, Howell, Stephen A, Martin, Stephen R, Knuepfer, Ellen, Taylor, Helen M, Grainger, Munira, Holder, Anthony A
• Format: Article
• Language: English
• Subjects: Animals; Antimalarials - pharmacology; Antimalarials - therapeutic use; Carbazoles - pharmacology; Carbazoles - therapeutic use; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Enzyme Inhibitors - pharmacology; Enzyme Inhibitors - therapeutic use; Indole Alkaloids - pharmacology; Indole Alkaloids - therapeutic use; Malaria, Falciparum - drug therapy; Malaria, Falciparum - enzymology; Malaria, Falciparum - genetics; Membrane Proteins - genetics; Membrane Proteins - metabolism; Phosphorylation - drug effects; Plasmodium falciparum - enzymology; Plasmodium falciparum - genetics; Protein Kinases - genetics; Protein Kinases - metabolism; Protein Synthesis, Post-Translational Modification, and Degradation; Protozoan Proteins - antagonists & inhibitors; Protozoan Proteins - genetics; Protozoan Proteins - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M803129200

Calcium-dependent protein kinases (CDPKs) of Apicomplexan parasites are crucial for the survival of the parasite throughout its life cycle. CDPK1 is expressed in the asexual blood stages of the parasite, particularly late stage schizonts. We have identified two substrates of Plasmodium falciparum CDPK1: myosin A tail domain-interacting protein (MTIP) and glideosome-associated protein 45 (GAP45), both of which are components of the motor complex that generates the force required by the parasite to actively invade host cells. Indirect immunofluorescence shows that CDPK1 localizes to the periphery of P. falciparum merozoites and is therefore suitably located to act on MTIP and GAP45 at the inner membrane complex. A proportion of both GAP45 and MTIP is phosphorylated in schizonts, and we demonstrate that both proteins can be efficiently phosphorylated by CDPK1 in vitro. A primary phosphorylation of MTIP occurs at serine 47, whereas GAP45 is phosphorylated at two sites, one of which could also be detected in phosphopeptides purified from parasite lysates. Both CDPK1 activity and host cell invasion can be inhibited by the kinase inhibitor K252a, suggesting that CDPK1 is a suitable target for antimalarial drug development.