Article
CDK-like kinases of the Plasmodium falciparum blood stages are involved in phosphorylation of splicing factor
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Authors
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S. Kern
- Institute for Molecular Biotechnology, RWTH Aachen University, Aachen, Germany; Research Center for Infectious Diseases, University of Würzburg, Würzburg, Germany
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S. Agarwal
- Institute for Molecular Biotechnology, RWTH Aachen University, Aachen, Germany; Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, Scotland, UK
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J. Halbert
- Research Center for Infectious Diseases, University of Würzburg, Würzburg, Germany; Inserm-EPFL Joint Laboratory, Global Health Institute, Lausanne, Switzerland
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F. Bracher
- Department of Pharmacy – Center for Drug Research, Ludwig-Maximilians University, Munich, Germany
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J. M. Przyborski
- Parasitology, Faculty of Biology, Phillips University Marburg, Marburg, Germany
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T. Dandekar
- Bioinformatics, University of Würzburg, Biocenter, Würzburg, Germany
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C. Doerig
- Inserm-EPFL Joint Laboratory, Global Health Institute, Lausanne, Switzerland; Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, Scotland, UK; Department of Microbiology, Monash University, Wellington Road, Clayton, Australia
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R. Fischer
- Institute for Molecular Biotechnology, RWTH Aachen University, Aachen, Germany
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G. Pradel
- Institute for Molecular Biotechnology, RWTH Aachen University, Aachen, Germany
| Published: | January 8, 2013 |
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Outline
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The kinome of the human malaria parasite Plasmodium falciparum comprises representatives of most eukaryotic protein kinase groups, including kinases which regulate proliferation and differentiation processes. Despite extensive research on most plasmodial enzymes, little information is available regarding the four identified members of the cyclin¬dependent kinase-like kinases (CLK) family. In other eukaryotes, CLKs regulate mRNA splicing through phosphorylation of Serine/Arginine-rich proteins. Here we investigate the PfCLKs, the Lammer kinase homologue PfCLK-1 (PF3D7_1445400), PfCLK-2 (PF3D7_1443000), PfCLK-3 (PF3D7_1114700) and PfCLK-4/SRPK-1 (PF3D7_0302100). All four PfCLKs show homology with the yeast Serine/Arginine protein kinase Sky1p and are transcribed throughout the asexual blood stages as well as in gametocytes. PfCLK-1/Lammer possesses two nuclear localization signal sites and PfCLK-2 possesses one of these signal sites upstream of the C-terminal catalytic domains. Indirect immunofluorescence and Western Blot Data confirm that the kinases are primarily localized in the parasite nucleus and in the cytoplasm. In vitro kinase assays show substrate phosphorylation by the PfCLKs, including the Sky1p substrate, yeast splicing factor Npl3p, and the plasmodial splicing factors PfASF-1 (PF3D7_1119800), PfSR-1 (PF3D7_0503300) and PF3D7_1022400. Inhibitors of human/microbe CLKs inhibit growth of the P. falciparum blood stages in the low micromolar range. In addition, preliminary findings show inhibitory effects of these inhibitors on parasite gametogenesis. Our data indicate a crucial role of PfCLKs predominantly for malaria blood stage parasites, presumably by participating in gene regulation through the post-transcriptional modification of mRNA.
