Involvement of Protein Kinase C-Dependent Mitogen-Activated Protein Kinase p44/42 Signaling Pathway for Cross-Talk between Estradiol and Transforming Growth Factor-β3 in Increasing Basic Fibroblast Growth Factor in Folliculostellate Cells

Abstract

AbstractWe have recently shown that TGF-β3, in the presence of estradiol, increases the release of basic fibroblast growth factor (bFGF) from folliculostellate (FS) cells in the pituitary. We determined the interactive effects of TGF-β3 and estradiol on bFGF production and release from FS cells, and the role of the MAPK pathway in TGF-β3 and estradiol interaction. We found that TGF-β3 and estradiol alone moderately increased cell content and release of bFGF from FS cells; but together, they markedly increased the peptide. Estradiol and TGF-β3 alone moderately activated MAPK p44/42; together they produced marked activation of MAPK p44/42. Pretreatment of FS cells with an MAPK kinase 1/2 inhibitor or with protein kinase C inhibitors suppressed the activation of MAPK p44/42, bFGF release, and protein level increases, all of which were induced by TGF-β3 and estradiol. Estradiol and TGF-β3, either alone or in combination, increased the levels of active Ras. Furthermore, bFGF induction by TGF-β3 and estradiol was blocked by overexpression of Ras N17, a dominant negative mutant of Ras p21. Estrogen receptor blocker ICI 182,780 failed to prevent estrogen’s and TGF-β3’s effects on bFGF. These data suggest that an estradiol receptor-independent protein kinase C- activated Ras-dependent MAPK pathway is involved in the cross-talk between TGF-β3 and estradiol to increase bFGF production and/or release from FS cells.