Establishment of cell-cell junctions depends on the oligomeric states of VE-cadherin.

Specifically expressed at intercellular adherens junctions of endothelial cells, VE-cadherin is a receptor that exhibits particular self-association properties. Indeed, in vitro studies demonstrated that the extracellular part of VE-cadherin elaborates Ca(++)-dependent hexameric structures. We hypothesized that this assembly could be at the basis of a new cadherin-mediated cell-cell adhesion mechanism. To verify this assumption, we first demonstrated that VE-cadherin can elaborate hexamers at the cell surface of confluent endothelial cells. Second, mutations were introduced within the extracellular part of VE-cadherin to destabilize the hexamer. Following an in vitro screening, three mutants were selected, among which, one is able to elaborate only dimers. The selected mutations were expressed as C-terminal green fluorescent protein fusions in CHO cells. Despite their capacity to elaborate nascent cell-cell contacts, the mutants seem to be rapidly degraded and/or internalized. Altogether, our results suggest that the formation of VE-cadherin hexamers protects this receptor and might allow the elaboration of mature endothelial cell-cell junctions.