JAK3-Mediated Structural Remodeling of β-Catenin Suppresses Epithelial–Mesenchymal Transition: Insights from In Silico Modeling

Introduction: Janus kinase 3 (JAK3) is a non-receptor tyrosine kinase that phosphorylates multiple proteins, including β-catenin, a critical component of adherens junctions (AJs). We previously demonstrated that JAK3-mediated phosphorylation of β-catenin regulates its basolateral localization and preserves epithelial barrier integrity. However, the structural basis underlying JAK3–β-catenin interactions and their role in epithelial–mesenchymal transition (EMT) remains unclear. Methodology: Here, we employed homology modeling, molecular docking, and structural simulations to investigate phosphorylation-dependent interactions between JAK3 and β-catenin. Results: Our analysis revealed that Src-mediated phosphorylation at Y654 induces conformational remodeling of the β-catenin N-terminal domain (NTD), creating a favorable interface for JAK3 binding and shifting its interaction from the armadillo repeat domain to the NTD. Subsequent JAK3-mediated phosphorylation at Y30, Y64, and Y86 restores β-catenin conformation, stabilizes the E-cadherin/β-catenin complex, and limits nuclear translocation. Phosphomimetic analyses identified distinct structural contributions of these residues. Conclusions: Collectively, these findings reveal a sequential Src–JAK3 phosphorylation mechanism that maintains AJ integrity and suppresses EMT, providing potential therapeutic insights into epithelial cancer progression.