The beta 4 integrin subunit is expressed in mouse fibroblasts and modulated by transforming growth factor-beta 1

Integrin beta 4 subunit is present in association with alpha 6 chain on both normal and transformed epithelial cells. Recently alpha 6 beta 4 heterodimer was found on the endothelium of medium-sized blood vessels and on immature thymocytes. In this report we show, by Northern blotting, indirect immunofluorescence, immunoprecipitation, and Western blotting, that beta 4 subunit is expressed also on cells of mesenchymal origin such as fibroblasts, myoblasts, and myotubes. Increased expression of alpha 6 beta 4 has been related to the aggressive metastatic phenotype of human and murine carcinomas. The transforming growth factor beta 1 (TGF-beta 1) has been found to modulate the expression of several integrins and intracellular matrix proteins, as well as to stimulate cell invasion and metastatic potential. To evaluate whether alpha 6 beta 4 expression is modulated by TGF-beta 1, we transfected 3T3 fibroblasts with an expression vector carrying the human TGF-beta 1 cDNA driven by the SV40 early promoter. We observed by indirect immunofluorescence a modification in the subcellular distribution of beta 4 subunit, which acquires a perinuclear localization. This finding suggests this integrin subunit correlates with the cytoskeletal reorganization induced by TGF-beta 1.