Human vascular endothelial cadherin (VE-cadherin, 7B4/cadherin-5) is an endothelial-specific cadherin localized at the intercellular junctions. To directly investigate the functional role of this molecule we cloned the full-length cDNA from human endothelial cells and transfected its coding region into Chinese hamster ovary cells. The product of the transfected cDNA had the same molecular weight as the natural VE-cadherin in human endothelial cells, and reacted with several VE-cadherin mouse monoclonal antibodies. Furthermore, it selectively concentrated at intercellular junctions, where it codistributed with alpha-catenin. VE-cadherin conferred adhesive properties to transfected cells. It mediated homophilic, calcium-dependent aggregation and cell-to-cell adhesion. In addition, it decreased intercellular permeability to high-molecular weight molecules and reduced cell migration rate across a wounded area. Thus, VE-cadherin may exert a relevant role in endothelial cell biology through control of the cohesion and organization of the intercellular junctions.

In vivo, intact endothelium presents a low turnover rate, however, when junctions are disrupted cells gain the capacity to migrate and proliferate. This capacity is then lost when cell to cell contacts are reorganized (4).Endothelial cell junction components are therefore good candidates for transferring migration and growth inhibitory signals. Previous work (5) showed that protein membrane extracts from confluent endothelial cells were able to inhibit the growth of sparse endothelium but not of other cell types, suggesting the existence of membrane associated endothelial growth inhibitory proteins.It was previously found that endothelial cells express a cell specific member of the cadherin family (cadherin-5 or vascular endothelial cadherin [VE-cadherin]) 1 (6)(7)(8). This molecule is so far the only cadherin consistently organized at interendothelial adherence junctions (8-10). VE-cadherin is a constitutive component of all types of endothelia (8). As the other members of the family (11-15), VE-cadherin has adhesive properties and mediates homotypic cell adhesion (16). The intracellular domain interacts with cytoplasmic proteins called catenins (17) that transmit the adhesion signal and contribute to the anchorage of the protein to the actin cytoskeleton (18,19).In other types of tissues, cadherins can act as tumor suppressors. Reduced cadherin expression and/or activity is associated with enhanced tumor cell invasive potential and loss of differentiated characteristics (11)(12)(13)(14)(15)(18)(19)(20)(21)(22)(23). In agreement with these observations, VE-cadherin expression was found to be strongly reduced in angiosarcomas (24).In this paper we investigated the effect of VE-cadherin on cell growth. The results reported show that VE-cadherin can indeed transfer growth negative signals to the cells. This molecule can therefore contribute to density dependent inhibition of endothelial cell growth. MethodsCells. Human endothelial cells from umbilical vein (HUVEC) were isolated and cultured in M199 and 20% NCS (newborn calf serum) as previously described (8). Chinese hamster ovary (CHO) cells and mouse connective tissue fibroblast L929 cells were obtained from the American Tissue Type Collection and cultured in DMEM with 10% FCS (both from GIBCO, Life Technologies, Paisley, U.K.) (16). Full length VE-cadherin cDNA was cloned from human endothelial cells and inserted into pECE eukaryotic expression vector. CHO and L929 cells were cotransfected with pECE-VE-cadherin construct and pSV 2 neo plasmids by calcium phosphate precipitation as described (16). Control cells were transfected with empty pECE and pSV 2 neo plasmids, selected, cloned, and cultured as VE-cadherin transfectants (16). VE-cadherin expression in the clones used was comparable with that of HUVEC by Western and Northern blot analysis (16).For transfection of CHO cells with truncated VE-cadherin, full length VE-cadherin cDNA cloned in pBluescript vector (16)