VEGF stimulates tyrosine phosphorylation of β-catenin and small-pore endothelial barrier dysfunction.

The purpose of this study was to test the hypothesis that tyrosine phosphorylation signaling events and protein kinase C (PKC) activation mediate vascular endothelial growth factor-A165 (VEGF)-induced endothelial cell (EC) proliferation and barrier dysfunction in bovine pulmonary artery EC monolayers. A size-selective permeability assay showed that VEGF stimulated a delayed, prolonged (6-45 h), concentration-dependent (50-200 ng/ml, ∼1-4 nM) increase in the number of predominantly small-"pore" transport pathways (<60 Å) across EC monolayers. The tyrosine kinase inhibitor herbimycin A (HA) and the selective PKC inhibitor bisindolylmaleimide (BIM) prevented this phenomenon. After 6-24 h, VEGF-treated monolayers displayed an HA- and BIM-sensitive reorganization of β-catenin adherens junctions with fingerlike projections and the loss of β-catenin at sites of small paracellular hole formation. HA and BIM prevented the VEGF-induced increase in EC growth. HA blocked the VEGF-induced rapid and prolonged (10 min-45 h) increases in the phosphotyrosine (PY) contents of VEGF receptor 2, phospholipase C-γ1, paxillin, and β-catenin as well as ∼140- and 128- to 117-kDa proteins, whereas BIM inhibited only the tyrosine phosphorylation of β-catenin. These data suggest that VEGF initiates increased EC growth and chronic, small-pore endothelial barrier dysfunction by PY signaling through β-catenin that depends on PKC.