ELUCIDATION OF A SIGNALING PATHWAY INDUCED BY FGF-2 LEADING TO UPA GENE-EXPRESSION IN NIH 3T3 FIBROBLASTS

Fibroblast growth factors (FGFs) play a role in biological processes s uch as cell growth and development, angiogenesis, and wound healing. S everal genes have been shown to be induced by FGFs, but the underlying mechanisms have not been elucidated. We investigated the effect of FG F-2 (basic FGF) on the urokinase-type plasminogen activator (uPA) gene in NIH 3T3 fibroblasts. We found that the uPA gene is transcriptional ly induced by FGF-2 as well as by 12-0-tetradecanoylphorbol-1 3-acetat e involving a PEA3/AP1 element located 2.4 kb upstream of the transcri ption initiation site; neither induction requires ongoing protein synt hesis. Unlike 12-O-tetradecanoylphorbol-13-acetate induction, FGF-2 in duction was not impaired by protein kinase C down-regulation. Analyses of various signaling molecules by Western blotting, extracellular sig nal-regulated kinase (ERK) activity assays, and transient transfection assays (cotransfection of a uPA-reporter gene construct with expressi on vectors for wild-type or dominant negative type of these molecules or for ERK-specific protein phosphatase MKP-1) showed that a Ras/Raf-1 /MEK/ERK-2/JunD pathway is induced by FGF-2 and 12-O-tetradecanoylphor bol-13-acetate, leading to the activation of the uPA gene.