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Abstract
In the preceding report, experiments were described which identify the 2A10 antigen of retinal pigment epithelial (RPE) cells as a beta 1 subunit of the cell-surface extracellular matrix receptor protein integrin. In this article, experiments are presented which use the 2A10 and CSAT antibodies, both directed against the beta 1 subunit, to investigate the role of integrin in RPE and fibroblast (FB) cell-substrate adhesion. When added to cultures simultaneously with cells, either the 2A10 or CSAT antibodies inhibit both FB and RPE cell adhesion and spreading on laminin (LM). However, although the 2A10 antibody blocks adhesion and spreading of FB and RPE cells on fibronectin (FN), the CSAT antibody has no effect. The inhibition of the 2A10 antibody is specific for integrin-mediated adhesion; it does not affect FB or RPE cell adhesion and spreading on tissue-culture plastic. When RPE cells are first allowed to attach to and spread on FN and LM and then the 2A10 or CSAT antibody is added to the cultures, both cause detachment and rounding of RPE cells from LM, but neither has any effect on the cells already spread on FN. These results indicate that there are differences in the way FB and RPE cells interact with LM and FN. Furthermore, these results provide the first direct functional demonstration that RPE cell-substrate adhesion is mediated by integrin.