Long-range and selective autoregulation of cell-cell or cell-matrix adhesions by cadherin or integrin ligands

In this study we demonstrate that local stimulation of cell surface cadherins or integrins induces al enhancement of adherens junction or focal assembly, respectively, throughout the cell, IV-cadherin transfected CHO cells (CHO-Ncad) were incubated with different ligands including N-cadherin extracellular domain (NEC), anti-N-cadherin antibodies, fibronectin and concanavalin A (ConA), conjugated to synthetic beads, Electron microscopic examination indicated that both cadherin-and integrin-reactive beads bound tightly to the cell surface and were apparently endocytosed after several hours of incubation, The ConA-beads remained largely at the cell surface, Immunofluorescence labeling of the cells with antibodies to different adhesion-associated molecules indicated that both NEC- and anti-N-cadherin-conjugated beads induced a major increase in the level of junction-associated cadherin and beta-catenin labeling and a modest increase in junctional vinculin labeling, compared to untreated cells or cells bound to ConA-bleads. FN-conjugated beads, on the other hand, significantly enhanced vinculin labeling at focal contacts and suppressed cadherin and beta-catenin staining in cell-cell junctions, The cadherin-reactive beads specifically stimulated tyrosine phosphorylation at cell-cell junctions, while the FN-beads increased the levels of focal contact-associated phosphotyrosine, as shown by immunofluorescence labeling of the cells for phosphotyrosine, Inhibition of this phosphorylation by genistein resulted in a complete suppression of the effects of both types of beads. These findings indicate that specific cadherin- and integrin-mediated surface interactions can trigger positively cooperative long-range signaling events which lead to the selective assembly of cell-cell or cell-matrix adhesions, and that these signals involve tyrosine phosphorylation.