Structure-Based Computational Dissection of Angiopoietin2-Tie2 Interaction Determinants

Angiopoietin2 (Ang2) is a crucial growth factor in vasculogenic and angiogenic processes, such as embryo vascular formation, wound repair, blood clotting, and tumor growth. Ang2 binds and activates the receptor tyrosine kinase (RTK) Tie2, which in turn activates downstream signaling cascades. We used structure-based computational methods to predict and explain the mechanistic effect of mutations in Ang2 and Tie2 on their interactions. We use physics-based approaches to pinpoint direct per-residue contributions to protein-protein interactions and to identify residues that upon mutation will influence the protein’s tertiary structure and thereby indirectly affect protein-protein interactions.

We identified a small subset of Ang2 and Tie2 residues that make substantial contributions to their interactions. We also identified a larger set of residues that are substantially buried in the core of Ang2. These residues can therefore modify the tertiary structure of Ang2 when mutated, and thereby interactions with Tie2 indirectly. We validated our computational predictions using random and directed mutagenesis and yeast display, showing that our calculations predicted almost all of the experimental results accurately. Analysis of additional RTK-ligand complexes further validates the utility of our approach.

This approach is a generalizable method to pinpoint residues whose missense mutations can affect protein-protein interactions. Our results can direct the redesign and further research of Ang2 and Tie2, and can be applied to analyze additional RTKs and their ligands. Moreover, our findings can guide the development of therapeutics for a variety of diseases such as cancer, which result from mutations leading to faulty receptor-ligand binding.