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-s ubstrate signal transduction. It was hypothesized that while primary c orneal epithelial cells seeded onto laminin and fibronectin express an d synthesize integrin receptors, they are not detected on the plasma m embrane until the appropriate ligand is present. The integrin subunits (alpha-6, beta-4 and beta-1) present on the plasma membrane after adh erence to laminin and fibronectin were compared with changes that occu rred in mRNA expression and protein synthesis. Prior to seeding, the p ercentage of cells expressing integrin receptors and matrix proteins o n their plasma membrane was determined. Negligible laminin and fibrone ctin (0-7 %) were present on the plasma membrane while the population of epithelial cells expressing beta-4 and beta-1 on the plasma membran e was low (21-23 %). After 3 hr of adherence the cell population expre ssing integrin subunits was substrate dependent. The percentage of cel ls adherent to LM expressing beta-4 was four-fold greater than cells a dherent to FN. After 24 hr the percentage of cells cultured on fibrone ctin expressing beta-4 increased significantly indicating ligand depos ition. 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 n ot detected until 18 hr on LM and 21 hr on FN. The present results dem onstrate that expression and transport of integrin receptors to the pl asma membrane of primary corneal epithelial cells after adhesion is re gulated by the presence of specific ligands. (C) 1997 Academic Press L imited.