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doi: 10.1242/10.1242/jcs.00154

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Protein kinase CKII regulates the interaction of ß-catenin with -catenin and its protein stability

Stephan Bek^* and Rolf Kemler

Department of Molecular Embryology, Max-Planck Institute of Immunobiology, Stuebeweg 51, D-79108 Freiburg, Germany
^* Present address: Stephan Bek, Aventis Pharma Deutschland, Functional Genomics, Industriepark Hoechst, G879/029, D-65926 Frankfurt/Main, Germany

Author for correspondence (e-mail: kemler{at}immunbio.mpg.de)

Accepted 9 September 2002

ß-Catenin is a multi-functional cellular component and a substrate for several protein kinases. Here we investigated the interaction of protein kinase CKII (casein kinase II) and ß-catenin. We show that CKII phosphorylates the N-terminal region of ß-catenin and we identified Ser29, Thr102, and Thr112 as substrates for the enzyme. We provide evidence that CKII regulates the cytoplasmic stability of ß-catenin and acts synergistically with GSK-3ß in the multi-protein complex that controls the degradation of ß-catenin. In comparing wild-type and Ser/Thr-mutant ß-catenin, a decreased affinity of the mutant protein to -catenin was observed. Moreover, kinase assays in vitro demonstrate a CKII-dependent increase in the binding of wild-type ß-catenin with -catenin. In line with that, cells expressing Ser/Thr-mutant ß-catenin exhibit an increased migratory potential, which correlates with an enhanced cytosolic localization and a reduced association with the cytoskeleton of the mutant protein. From these results we conclude that CKII regulates the function of ß-catenin in the cadherin adhesion complex as well as its cytoplasmic stability.

Key words: Casein kinase II, ß-Catenin, -Catenin, Protein kinase, Caderin adhesion complex