Targeting the Tcf4 G¹³ANDE¹⁷ binding site to selectively disrupt β-Catenin/T-Cell factor protein?protein interactions

Selective disruption of protein protein interactions by small molecules is important for probing the structure and dynamic aspects of cellular network. It can also provide new therapeutic targets. β-Catenin of the canonical Wnt signaling pathway uses the same positively charged groove to bind with T-cell factor (Tcf), cadherin, and adenomatous polysis coli (APC). The extravagant formation of β-catenin/Tcf interactions drives the initiation and progression of many cancers and fibroses, while β-catenin/ cadherin and β-catenin/APC interactions are essential for cell cell adhesion and β-catenin degradation. In this study, a selective binding site that can differentiate β-catenin/Tcf, β-catenin/cadherin, and β-catenin/APC interactions was identified by alanine scanning and biochemical assays. A new peptidomimetic strategy that incorporates SiteMap and multiple-copy simultaneous search was used to design selective small-molecule inhibitors for β-catenin/Tcf interactions. A potent inhibitor was discovered to bind with β-catenin and completely disrupt β-catenin/Tcf interactions. It also exhibits dual selectivity for β- catenin/Tcf over β-catenin/cadherin and β-catenin/APC interactions in both biochemical and cell-based assays. This study provides a proof of concept for designing selective inhibitors for β-catenin/Tcf interactions.