The role of beta-Arrestin in achieving Wnt-signaling specificity

• Applicant: Professorin Dr. Alexandra Schambony
• Subject Area: Developmental Biology ; Cell Biology
• Term: from 2008 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 90867295

The Wnt family of secreted morphogens activates divergent signaling cascades, which are traditionally divided into one canonical Wnt/beta-Catenin pathway and multiple non-canonical beta-Catenin-independent pathways. The different Wnt pathways are intimately linked by interactions, cross-talk and antagonistic regulation, which led to the emerging opinion that Wnt signaling might be a signaling network rather than a group of distinct pathways. Our joint proposal for the first funding period was based on the hypothesis that beta-Arrestin 2 (Arrb2) is a central protein in different Wnt pathways that interacts with different binding partners and thereby contributes to signal specificity and signal integration. Indeed, we observed that beta-Arrestin 2 forms a core complex with Dishevelled that is required for signal transduction and that is modulated by G (beta/gamma) and links the major intracellular modules activated by Wnt/Frizzled receptor complexes. By quantitative functional proteomics we have characterized the protein-protein interactions of this beta-Arrestin / Dishevelled core complex and identified new interacting proteins and also new physical interactions with known modulators of Wnt signaling. Further, in the course of follow-up experiments on the novel physical interaction between CamKII and Dishevelled 2 (Dvl2), we observed differential binding of CamKII to Dvl1, Dvl2 and Dvl3. Strikingly, these differential physical interactions were related to non-redundant, partially antagonistic biological functions of the three Dvl paralogs in Wnt/Ca2+ signaling. In this renewal application, I propose to analyze a set of novel kinases, phosphatases and scaffold proteins that we have identified as interactors of the Arrb2/Dvl2 core complex with respect to their putative role as modulators of the Wnt signaling network and the underlying molecular mechanisms. In addition, the striking indication that the three Dvl paralogs may form distinct protein complexes poses the question how different protein complex compositions relate to functional divergence and I intend to investigate in more detail. To achieve this aim we propose in addition to establish an in vivo read-out system for synchronous, multiplexed monitoring of kinase activity in Wnt pathways by quantitative mass spectrometry.

• DFG Programme: Research Grants