Biochemical and Biophysical Research Communications, Vol.284, No.1, 33-41, 2001
Downregulated expression of integrin alpha 6 by transforming growth factor-beta(1) on lens epithelial cells in vitro
Integrins represent the main cell surface receptors that mediate cell-matrix and cell-cell interactions. They play critical roles in adhesion, migration, morphogenesis, and the differentiation of several cell types. Previous studies have demonstrated that members of the fibroblast growth factor (TGF)-beta (1), transforming growth factor (TGF)-beta (1), and insulin growth factor (IGF)-1 play important roles in lens biology. In particularly, TGF-beta (1) appears to play a key role in extracellular matrix production, cell proliferation, and cell differentiation of lens epithelial cells. In this study we investigated the effects of FGF-2, TGF-beta (1), and IGF-1 on the modulation of integrin receptors using lens epithelial cell lines (HLE B-3 and alpha TN-4) and lens explants. We found that the expression of integrin alpha6 is downregulated by TGF-beta (1), but is not responsive to FGF-2 or IGF-1. The promoter activity of the integrin a6 gene decreased upon TGF-beta (1) treatment in a transient transfection assay, and flow cytometric analysis demonstrated the reduced expression of integrin alpha6 by TGF-beta (1), whereas significant changes were not observed in the level of integrin a6 after the addition of FGF-2. These findings suggest that the reduced Expression of integrin alpha6 caused by TGF-beta (1) might play a role in the activation of the cell cycle genes required during the fiber differentiation of the lens.
Keywords:integrin;transforming growth factor-beta 1;(TGF-beta(1));promoter;gene regulation;differentiation