Comparative phosphoproteome analysis suggests targets of casein kinase 1 in Chlamydomonas reinhardtii flagella

Jens Boesger, Volker Wagner, Wolfram Weisheit, and Maria Mittag

Institute of General Botany and Plant Physiologie, Friedrich Schiller University Jena, Am Planetarium 1, 07743 Jena, Germany

Proteome analysis revealed the presence of several kinases and protein phosphatases in the flagella of Chlamydomonas reinhardtii (1). Reversible protein phosphorylation can control ciliary beating, motility, signaling, length and assembly. Recently, we could identify 141 flagellar phosphopeptides by mass spectrometry. These belong to different structural and motor proteins, kinases, proteins with protein interaction domains as well as many proteins, whose function is still unknown (2). In several cases, a dynamic phosphorylation pattern and clustering of phosphorylation sites was found, indicating a complex and site specific control by reversible protein phosphorylation in the flagellum. These processes involve kinases, like casein kinase 1 (CK1). CK1 regulates dynein activity and flagellar motility (3). Silencing of CK1 alters flagella formation and circadian phototaxis of C. reinhardtii (4). To find targets of CK1, we applied a specific inhibitor (CK1-7) against this kinase and analyzed the flagellar phosphoproteome under these conditions. In this approach, some structural and other phosphoproteins are missing in comparison to the wild type phosphoproteome. In addition, we found new phosphorylated proteins, including kinases. These data indicate that CK1 is part of a regulatory network of different kinases in the flagellum. (1) Pazour et al., 2005, J Cell Biol 170:103-13; (2) Boesger et al., 2009, Eukaryot Cell 8:922-32; (3); Gokhale et al., 2009, J Cell Biol 186:817-24; (4) Schmidt et al., 2006, Plant Cell 18:1908-30.

e-mail address of presenting author: jens.boesger@uni-jena.de