Abstract 337: VE-Cadherin Mechanotransduction Regulates Lung Endothelial Contractility and Barrier Integrity

Abstract

Dysfunctional regulation of endothelial adherens junctions is the direct underlying cause of vascular leak and pulmonary edema in acute lung injury. Indirect evidence suggests that cytoskeletal rearrangements are linked to adherens junction remodeling, but there is no clear demonstration that adherens junction proteins play an active role in the regulation of intracellular or extracellular mechanical tension. Here I investigate mechanotransduction (response to applied force) of VE-cadherin, the main structural protein at adherens junctions, and how this regulates global cell contractility and actin remodeling both locally and globally. Mechanical responses in human pulmonary artery endothelial cells were studied using magnetic twisting cytometry (MTC) experiments, in which shear stress was exerted on specific cell surface receptors by twisting magnetized beads bound to the cell surface. Remodeling of adherens junctions and F-actin in response to mechanical force was visualized by immunofluorescence. Confocal microscopy revealed force-actuated changes in both local and global cytoskeletal organization, as well as local rearrangements at both bead-cell and cell-cell junctions. This force-dependent remodeling correlated directly with the stiffening of VE-cadherin junctions with increasing applied stress. Treatment with cytoskeletal inhibitors significantly diminished this response. When a constant magnitude of shear stress was applied continuously over time, VE-cadherin junctions increased stiffness, suggesting active junction reinforcement. These data provide direct evidence that VE-cadherin complexes are tension sensors, and that associated mechanotransduction regulates global cell mechanics. Moreover, I present data showing that cadherin adhesions across the cell monolayer form a mechanically coupled network that regulates the endothelial barrier in response to force. This suggests a new mechanism regulating endothelial monolayer integrity.