N‐cadherin strengthens VE‐cadherin adhesion through Trio/Rac1 signaling

Abstract

The vascular endothelium is comprised of a monolayer of endothelial cells (ECs) lining the blood vessels, which functions as a semi‐permeable barrier between blood and the surrounding tissue. Vascular Endothelial (VE)‐cadherin, which forms homotypic adhesions between ECs at adherens junctions (AJs), is the main adhesive molecule that restricts the passage of protein rich fluids across the endothelial monolayer. Along with VE‐cadherin, ECs express Neural (N)‐cadherin, which is excluded from AJs but forms heterotypic adhesions between ECs and mural cells at the abluminal surface of the endothelium. While the role of VE‐cadherin adhesion in regulating endothelial barrier function has been well established, the role of N‐cadherin in ECs remains mainly unknown. We have demonstrated that inducible deletion of Cdh2 gene (encoding N‐cadherin in endothelial cells of adult mice) results in increased permeability of the endothelial vessel wall to albumin in the lung, brain, and kidney. Consistent with these results, accumulation of VE‐cadherin at AJs in endothelial cells of N‐cadherin EC‐KO mice in vivo was significantly reduced. To investigate N‐cadherin adhesion‐mediated signaling in endothelial monolayers, we covalently attached the extracellular domain of N‐cadherin to an Ni‐NTA surface in an oriented manner. N‐cadherin adhesion‐mediated signaling promoted recruitment of VE‐cadherin to AJs. Depletion of N‐cadherin in endothelial cells abolished this effect, suggesting that N‐cadherin adhesion‐mediated signaling promotes assembly of VE‐cadherin adhesion. Using a combination of N‐cadherin coated biomimetic platforms with mass spectroscopy, we isolated and analyzed N‐cadherin complexes. We found that a Rac1 activator, Trio, is recruited to N‐cadherin complexes to activate Rac1 signaling at AJs. This was consistent with formation of lamellipodia protrusions above AJs and increased Rac1 activity as determined by a Rac1 FRET biosensor. Depletion of Trio decreased recruitment of VE‐cadherin to AJs and resulted in a loss of Rac1 activity downstream of N‐cadherin adhesion. These data cumulatively demonstrate that N‐cadherin promotes assembly of VE‐cadherin adhesion through Trio/Rac1 signaling.Support or Funding InformationNIH R01 HL103922AHA 16PRE27260230