Segregation of VE-cadherin from the LBRC depends on the ectodomain sequence required for homophilic adhesion

Abstract

The lateral border recycling compartment (LBRC) is a reticulum of perijunctional tubulovesicular membrane that is continuous with the plasmalemma of endothelial cells and is essential for efficient transendothelial migration (TEM) of leukocytes. The LBRC contains molecules involved in TEM, such as PECAM, PVR and CD99, but not VE-cadherin. Despite its importance, how membrane proteins are included in or excluded from the LBRC is not known. Immunoelectron microscopy and biochemical approaches demonstrate that inclusion into the LBRC is the default pathway for transmembrane molecules present at endothelial cell borders. A chimeric molecule composed of the extracellular domain of VEcadherin and cytoplasmic tail of PECAM (VE-CAD/PECAM) did not enter the LBRC, suggesting that VE-cadherin was excluded by a mechanism involving its extracellular domain. Deletion of the homophilic interaction domain EC1 or the homophilic interaction motif RVDAE allowed VE-CAD/PECAM and even native VEcadherin to enter the LBRC. Similarly, treatment with RVDAE peptide to block homophilic VE-cadherin interactions allowed endogenous VE-cadherin to enter the LBRC. This suggests that homophilic interactions of VE-cadherin stabilize it at cell borders and prevent entry into the LBRC.

Transendothelial migration: unifying principles from the endothelial perspective

“…The presence in the LBRC of all the molecules that positively regulate TEM and the fact that they move together during TEM begs the question of how these molecules can function sequentially in TEM? This is a focus of active research in our laboratory.…”

Localized signals that regulate transendothelial migration

“…PVR is also in the LBRC and, as expected, PVR mAb delivered to the LBRC blocked TEM [25]. How and why these molecules, all of which are together in the LBRC [15], regulate TEM sequentially is not known and is currently the subject of investigation.…”

“…The LBRC is a reticulum of 50 nm vesicular structures that are connected to each other and to the plasma membrane at intervals along the cell borders [11]. The LBRC contains a representative selection of lateral border membrane with the exception of VE-cadherin [13,14], which is actively excluded [15]. Membrane from the LBRC is moved by kinesin molecular motors along microtubules [16] to surround the leukocyte during its passage across the endothelial border during paracellular migration [11] and through the cell during transcellular migration [13].…”

Dephosphorylation of Y685-VE-Cadherin Involved in Pulmonary Microvascular Endothelial Barrier Injury Induced by Angiotensin II

“…As an endothelial specific adhesion protein located at adherens junctions, VE-cadherin played an important role in the maintenance of vascular integrity and endothelial barrier function [6]. Under specific microenvironments, cell-cell junction interruption may be induced after phosphorylation in the tyrosine residues of VE-cadherin [7, 8]. At the same time, skeletal rearrangement of the vascular endothelial cells could induce shrinkage of endothelial cells and elevation of endothelial interspace, which further hampered the function of vascular endothelial barrier [9].…”