RHO-PROTEIN REGULATES TIGHT JUNCTIONS AND PERIJUNCTIONAL ACTIN ORGANIZATION IN POLARIZED EPITHELIA

The rho family of GTP-binding proteins regulates actin filament organi zation. In unpolarized mammalian cells, rho proteins regulate the asse mbly of actin-containing stress fibers at the cell-matrix interface. P olarized epithelial cells, in contrast, are tall and cylindrical with well developed intercellular tight junctions that permit them to behav e as biologic barriers. We report that rho regulates filamentous actin organization preferentially in the apical pole of polarized intestina l epithelial cells and, in so doing, influences the organization and p ermeability of the associated apical tight junctions. Thus, barrier fu nction, which is an essential characteristic of columnar epithelia, is regulated by rho.