Urokinase-type plasminogen activator-mediated crosstalk between N-cadherin and β-Catenin promotes wound healing

Urokinase-type plasminogen activator (uPA) is a serine proteinase that in the central nervous system induces astrocytic activation. β-Catenin is a protein that links the cytoplasmic tail of cadherins to the actin cytoskeleton, thus securing the formation of cadherin-mediated cell adhesion complexes. Disruption of cell-cell contacts leads to the detachment of β-Catenin from cadherins, which is then degraded by the proteasome following its phosphorylation by GSK3β. Here we show that astrocytes release uPA following a scratch injury, and that this uPA promotes wound healing via a plasminogen-independent mechanism. We found that uPA induces the detachment of β-Catenin from the cytoplasmic tail of N-Cadherin (NCAD) by triggering its phosphorylation at Tyr654. Surprisingly, this is not followed by degradation of β-Catenin because uPA also induces the phosphorylation of the low density lipoprotein receptor-related protein 6 (LRP6) at Ser1490, which then blocks the kinase activity of GSK3β. Our work indicates that the ensuing cytoplasmic accumulation of β-Catenin is followed by its nuclear translocation and β-Catenin-triggered transcription of uPA's receptor (Plaur), which in turn is required for uPA to induce astrocytic wound healing.