β-Catenin phosphorylation at Y654 and Y142 is crucial for high mobility group box-1 protein-induced pulmonary vascular hyperpermeability.

Objective: Endothelial hyperpermeability is a hallmark of acute lung injury in response to sepsis. The imbalance between adherence junction (AJ) mediated cell-cell adherence forces and stress fiber driven contractile forces contributes to increased endothelial permeability. Here, we spotlight the effects of β-catenin Y654 andY142 phosphorylation on HMGB1-mediated endothelial barrier leakage.

Approach And Results: Our results showed that phospho-deficiencies at both β-catenin Y654and Y142ameliorated pulmonary vascular dysfunction in male C57 mice receiving a cecal ligation and puncture operation. In vitro analysis indicated that high mobility group box-1 protein (HMGB1) triggered β-catenin Y654 and Y142 phosphorylation, causing β-catenin translocation and adherence junction (AJ) disruptions as well as cytoskeleton rearrangement. In addition,β-catenin Y654 dephosphorylation attenuated HMGB1-mediated dissociation of VE-cadherin/β-catenin and, hence, partially prevented endothelial hyperpermeability. β-catenin Y142 dephosphorylation abolished HMGB1-induced uncoupling of β-catenin and α-catenin, suppressed cytoskeletal reassembly and, hence, alleviated endothelial hyperpermeability. Further investigation demonstrated that RAGE and Src were required forβ-catenin Y654 phosphorylation in response to HMGB1, while FAK was responsible for HMGB1-triggered β-catenin Y142 phosphorylation.

Conclusions: In sum, this study revealed the role of β-catenin Y654 and Y142 phosphorylation in HMGB1-mediated endothelial hyperpermeability through dysregulation between adherence and contractile forces. This result advances understanding of the mechanisms underlying pulmonary vascular hyperpermeability in sepsis.