Regulation of endothelial cell adherens junctions by a ras-dependent signal transduction pathway

Adherens junctions, consisting of transmembrane cadherin molecules and their associated cytoplasmic α-, β-, and γ-catenin proteins, are thought to be critical for the development of stable cell adhesion and subsequent 3-dimensional tissue organization. In human endothelial cells there is a marked induction of γ-catenin levels when cells reach confluence. We demonstrate that expression of a dominant negative ras gene product (N17ras) via adenoviral mediated gene transfer inhibits the confluent-dependent rise in γ-catenin mRNA and protein levels. Consistent with its effects on overall γ-catenin levels, expression of N17ras also reduces the amount of γ-catenin associated with the adherens junction. Finally, although expression of N17ras under normal culture conditions produces no clear morphological phenotype, endothelial cells expressing a dominant negative ras gene product fail to form 3-dimensional, vascular-like structures when plated on reconstituted extracellular matrix.