Laminin synthesis and the adhesion characteristics of immortalized human corneal epithelial cells to laminin isoforms

We have studied the synthesis of laminins (Ln) and determined the specific integrins mediating the adhesion of immortalized human corneal epithelial cells to mouse Ln-1, and human Lns-5 and -10. Immunofluorescence microscopy of the cells demonstrated integrin alpha (2), alpha (3), alpha (6), beta (1) and beta (4) subunits, integrins alpha (6) and beta (4) being found in a typical 'leopard-skin' like manner. Immunoprecipitation studies showed that the cells produced alpha3, beta3 and gamma2 chains of Ln-5, but not Lns-1 or -10. In culture Ln-5 was found as small plaques beneath the adhering cells within 1 hr, while in 4 hr widely spread Ln-5 plaques were observed in colocalization with beta (4) integrin subunit. By using a quantitative cell adhesion assay and function-blocking monoclonal antibodies we showed that integrin beta (1) subunit plays a role in mediating corneal epithelial cell adhesion to mouse Ln-1. However, none of the available function-blocking antibodies to integrin alpha -subunits inhibited the adhesion. Integrin alpha (3)beta (1) complex mediated the adhesion of corneal epithelial cells to human Lns-5 and -10. Integrin complex alpha (3)beta (1), as well as laminin alpha (3) chain, was also shown to mediate cell adhesion to newly produced endogenous Ln-5. The present results show that integrin alpha (3)beta (1) complex mediates the adhesion of corneal epithelial cells to Lns-5 and -10, while a yet unknown integrin a subunit appears to play a role in the adhesion to Ln-1. The results also show that among corneal basement membrane laminins, Ln-5 is synthetized by epithelial cells while Ln-10 may be a product of keratocytes. (C) 2000 Academic Press.