Myosin-dependent contractile activity of the actin cytoskeleton modulates the spatial organization of cell-cell contacts in cultured epitheliocytes

The spatial organization of cell-cell adherens junctions is distinct in cul tured cells from two different tissue types, specifically, epitheliocytes a nd fibroblasts, In epitheliocytes, contacts are localized tangentially, alo ng contacting cell edges and in association with circumferential actin bund les, Contacts between fibroblasts are radially oriented; that is, they are perpendicular to the overlapping edges of the cells and are associated with straight bundles of actin filaments. In the present study, we establish th at the spatial organization of cell-cell contacts in the epithelial cell li ne IAR-2 can be converted from the typical tangential pattern to the radial pattern observed in fibroblasts, This transition can be induced by treatme nt with two agents, phorbol 12-myristate 13-acetate and nocodazole, which h ave different modes of action. Inhibition of myosin contractility reverses tangential-to-radial conversion of cell-cell contacts. These data suggest t hat formation of radially aligned contacts depends on modulation of contrac tility within the actin cytoskeleton through the myosin motor protein. The results open the possibility that modulation of the spatial organization of cell-cell contacts may play important roles in regulating organization and physiological functions of epithelial tissues.