Structural Studies of the ß-Catenin Destruction Complex

The Wnt signaling pathway plays an important role during embryonic development. Tight control of the Wnt signaling pathway is essential and occurs largely through the regulation of free levels of the protein ß-catenin by the ß-catenin destruction complex. Misregulation of the Wnt signaling pathway is a common feature of severe human diseases such as cancers. However, the molecular mechanisms underlying ß-catenin destruction complex formation are largely unknown which is primarily due to the intrinsic flexibility of the involved protein complexes which renders them challenging to study using conventional structural techniques. Here we aim propose to use a combination of cutting-edge solution structural techniques to reveal the molecular mechanisms of ß-catenin trapping and phosphorylation by studying a minimal Axin-1 - GSK3ß - ß-catenin protein complex. This minimal complex contains all parts needed for ß-catenin trapping and phosphorylation. We aim to study structure and function of the Axin-1 - GSK3ß - ß-catenin complex, its (mis)regulation by post-translational modifications (PTMs, i.e. phosphorylation) and disease mutations, and its functional implications in cell-based assays. To overcome the challenges imposed by the intrinsic flexibility of the complex, we will make use of our recent methodological achievements for studying structure and dynamics of proteins and protein complexes, i.e. using a multi- disciplinary structural biology approach in which we combine frontier solution techniques such as Nuclear Magnetic Resonance (NMR) spectroscopy, Small-angle X-ray/neutron scattering (SAXS/SANS), and molecular modeling. Our structural and functional studies of the dynamic Axin-1 - GSK3ß - ß-catenin complex will not only provide biologically highly relevant insight into the allosteric regulation of the ß-catenin destruction complex and disease mechanisms, but also into the key role of disordered proteins in allosteric regulation.

The Wnt signaling pathway plays an important role during embryonic development. Tight control of the Wnt signaling pathway is essential and occurs largely through the regulation of free levels of the protein ß-catenin by the ß-catenin destruction complex. Misregulation of the Wnt signaling pathway is a common feature of severe human diseases such as cancers. However, the molecular mechanisms underlying ß-catenin destruction complex formation are largely unknown which is primarily due to the intrinsic flexibility of the involved protein complexes which renders them challenging to study using conventional structural techniques. Here we aim propose to use a combination of cutting-edge solution structural techniques to reveal the molecular mechanisms of ß-catenin trapping and phosphorylation by studying a minimal Axin-1 - GSK3ß - ß-catenin protein complex. This minimal complex contains all parts needed for ß-catenin trapping and phosphorylation. We aim to study structure and function of the Axin-1 - GSK3ß - ß-catenin complex, its (mis)regulation by post- translational modifications (PTMs, i.e. phosphorylation) and disease mutations, and its functional implications in cell-based assays. To overcome the challenges imposed by the intrinsic flexibility of the complex, we will make use of our recent methodological achievements for studying structure and dynamics of proteins and protein complexes, i.e. using a multi-disciplinary structural biology approach in which we combine frontier solution techniques such as Nuclear Magnetic Resonance (NMR) spectroscopy, Small-angle X- ray/neutron scattering (SAXS/SANS), and molecular modeling. Our structural and functional studies of the dynamic Axin-1 - GSK3ß - ß-catenin complex will not only provide biologically highly relevant insight into the allosteric regulation of the ß-catenin destruction complex and disease mechanisms, but also into the key role of disordered proteins in allosteric regulation.