Antagonistic Regulation of Tight Junction Dynamics by Glucocorticoids and Transforming Growth Factor- in Mouse Mammary Epithelial Cells

• Published in: The Journal of biological chemistry 1996-01, Vol.271 (1), p.404
• Main Authors: Paul L. Woo, Helen H. Cha, Karen L. Singer, Gary L. Firestone
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.1.404

The synthetic glucocorticoid, dexamethasone, stimulated the transepithelial electrical resistance and suppressed the DNA synthesis of 31EG4 nontransformed mouse mammary epithelial cells. The addition of transforming growth factor-β 1 (TGF-β) to mammary cells simultaneously with or up to 24 h after dexamethasone treatment prevented the steroid induction of transepithelial electrical resistance and stimulated the incorporation of [ 3 H]thymidine. However, the TGF-β inhibition of tight junction formation did not require de novo DNA synthesis. Confocal microscopy revealed that the organized immunostaining pattern of the tight junction protein, ZO-1, and F-actin at the cell periphery was disrupted by TGF-β, resulting in disorganized and diffuse staining patterns throughout the cell. Western blot analysis demonstrated that TGF-β did not alter the protein levels of ZO-1. In contrast to cells not treated or pretreated with steroid for up to 24 h, TGF-β had no effect on cells pretreated with dexamethasone for 48 h. Transfection of chimeric reporter genes containing promoters responsive to either glucocorticoid or TGF-β demonstrated that the mutual antagonism of tight junction dynamics by dexamethasone and TGF-β occurs in the presence of intact signaling pathways. Taken together, our results establish for the first time that glucocorticoids and TGF-β can antagonistically regulate tight junction formation in a nontransformed mammary cell line.