Self-assembly of the Vascular Endothelial Cadherin Ectodomain in a Ca2+-dependent Hexameric Structure

Abstract

Vascular endothelial cadherin (VE-cadherin) is a transmembrane protein essential for endothelial cell monolayer integrity (Gulino, D., Delachanal, E., Concord, E., Genoux, Y., Morand, B., Valiron, M. O., Sulpice, E., Scaife, R., Alemany, M., and Vernet, T. (1998) J. Biol. Chem. 273, 29786 -29793). This molecule belongs to the cadherin family of cell-cell adhesion receptors, for which molecular details of homotypic interactions are still lacking. In this study, a recombinant fragment encompassing the four N-terminal modules of VE-cadherin (VE-EC1-4) was shown to associate, in solution, as a stable Ca 2؉ -dependent oligomeric structure. Cross-linking experiments combined with mass spectrometry demonstrated that this oligomer is a hexamer. Gel filtration chromatography experiments and analytical ultracentrifugation analyses revealed the existence of an equilibrium between the hexameric and monomeric species of VE-EC1-4. The concentration at which 50% of VE-EC1-4 is in its hexameric form was estimated as 1 M. The dimensions of the hexamer, measured by cryoelectron microscopy to be 233 ؎ 10 ؋ 77 ؎ 7 Å, are comparable to the thickness of adherens endothelial cell-cell junctions. Altogether, the results allow us to propose a novel homotypic interaction model for the class II VEcadherin, in which six molecules of cadherin form a hexamer.

Modeling the Molecular Network Controlling Adhesion Between Human Endothelial Cells: Inference and Simulation Using Constraint Logic Programming

“…Adherens junctions in endothelial cells are constituted of VE-cadherin hexamers [16]. These VE-cadherins are membrane proteins with a cytoplasmic tail and a multidomain extracellular part.…”

Identification of Proteases Involved in the Proteolysis of Vascular Endothelium Cadherin during Neutrophil Transmigration

“…Based on our previous studies (11,12), we know that the extracellular module EC1 and the intact EC3-EC4 tandemmodule (amino acid stretch T212-E431) are both required for VE cadherin self-assembly. Consequently, at the endothelial cell surface, elastase and cathepsin G may cleave the VE cadherin molecule at positions identical to those observed for the recombinant fragment VE-EC1-5, thus probably destroying its hexameric assembly.…”

“…In an attempt to detect the proteases able to cleave VE cadherin, the cell culture supernatants were mixed with a recombinant protein encompassing the majority of the extracellular part of VE cadherin, designated as VE-EC1-4, which was previously demonstrated to be able to self-assemble as a stable hexamer (11,12).…”

“…VE cadherin participates in the elaboration of inter-endothelial adherens junctions as its extracellular part establishes homophilic interactions resulting in cellcell attachment (11,12). These ectodomain-based interactions are reinforced by interactions involving the cytoplasmic domain of VE cadherin, which binds, in a mutually exclusive manner, the armadillo proteins ␤ or ␥ catenin (13,14).…”

Sprouty2 expression controls endothelial monolayer integrity and quiescence

“…VEcadherins connect adjacent cells by forming hexamers [57,58]. VE-cadherins form trimers in cis at the cell surface and interact in trans with a trimer of a neighboring cell.…”