Casein kinase I phosphorylates the Armadillo protein and induces its degradation in Drosophila

摘要: Casein kinase I (CKI) was recently reported as a positive regulator of Wnt signaling in vertebrates and Caenorhabditis elegans. To elucidate the function Drosophila CKI wingless (Wg) pathway, we have disrupted its by double-stranded RNA-mediated interference (RNAi). While previous findings were mainly based on overexpression, this is first convincing loss-of-function analysis CKI. Surprisingly, CKIalpha- or CKIepsilon-RNAi markedly elevated Armadillo (Arm) protein levels Schneider S2R+ cells, without affecting mRNA levels. Pulse-chase showed that CKI-RNAi stabilizes Arm protein. Moreover, embryos injected with CKIalpha RNA naked cuticle phenotype, which associated activation Wg signaling. These results indicate functions negative Wg/Arm Overexpression induced hyper-phosphorylation both Dishevelled cells and, conversely, CKIalpha-RNAi reduced amount hyper-modified forms. His-tagged phosphorylated vitro set serine threonine residues are also Zeste-white 3. Thus, propose phosphorylates stimulates degradation.