Expression of integrin receptors on plasma membranes of primary corneal epithelial cells is matrix specific

Modulation of cell behavior may occur through cell adhesion receptors that bind domains of extracellular matrix molecules and mediate cell-substrate signal transduction. It was hypothesized that while primary corneal epithelial cells seeded onto laminin and fibronectin express and synthesize integrin receptors, they are not detected on the plasma membrane until the appropriate ligand is present. The integrin subunits (alpha-6, beta-4 and beta-1) present on the plasma membrane after adherence to laminin and fibronectin were compared with changes that occurred in mRNA expression and protein synthesis. Prior to seeding, the percentage of cells expressing integrin receptors and matrix proteins on their plasma membrane was determined. Negligible laminin and fibronectin (0-7 %) were present on the plasma membrane while the population of epithelial cells expressing beta-4 and beta-1 on the plasma membrane was low (21-23 %). After 3 hr of adherence the cell population expressing integrin subunits was substrate dependent. The percentage of cells adherent to LM expressing beta-4 was four-fold greater than cells adherent to FN. After 24 hr the percentage of cells cultured on fibronectin expressing beta-4 increased significantly indicating ligand deposition. The expression and protein synthesis of alpha-6 and beta-4 was evaluated and an increase in the synthesis of alpha-6 and beta-4 was not detected until 18 hr on LM and 21 hr on FN. The present results demonstrate that expression and transport of integrin receptors to the plasma membrane of primary corneal epithelial cells after adhesion is regulated by the presence of specific ligands. (C) 1997 Academic Press Limited.