PAPTi: a peptide aptamer interference toolkit for perturbation of protein-protein interaction networks.

Signaling proteins often form dynamic protein-protein interaction (PPI) complexes to achieve multi-functionality. Methods to abrogate a subset of PPI interfaces without depleting the full-length protein will be valuable for structure-function relationship annotations. Here, we describe the use of Peptide Aptamer Interference (PAPTi) approach for structure-function network studies. We identified peptide aptamers against Dishevelled (Dsh) and β-catenin (β-cat) to target the Wnt signaling pathway and demonstrate that these FN3-based MONOBODYs (FNDYs) can be used to perturb protein activities both in vitro and in vivo. Further, to investigate the crosstalk between the Wnt and Notch pathways, we isolated FNDYs against the Notch Ankyrin (ANK) region and demonstrate that perturbing the ANK domain of Notch increases the inhibitory activity of Notch towards Wnt signaling. Altogether, these studies demonstrate the power of the PAPTi approach to dissect specific PPI interactions within signaling networks.