Opposite and independent actions of cyclic AMP and transforming growth factor beta in the regulation of type 1 plasminogen activator inhibitor expression.
We have investigated the mechanisms by which type 1 plasminogen activator inhibitor (PAI-1) is regulated by transforming growth factor beta (TGF-beta) and by epidermal growth factor (EGF) in CCL64 mink lung epithelial cells, BSC-1 monkey kidney epithelial cells, mouse embryo fibroblast (AKR-2B 84A) cells and normal rat kidney fibroblasts (NRK). TGF-beta increases PAI-1 expression in all four cell lines, and EGF acts synergistically with TGF-beta to increase PAI-1 expression in CCL64 cells but not in the other three cell lines. Here we show that PAI-1 expression can be regulated independently through two different signal transduction pathways. One pathway involves protein kinase C and is stimulated by the tumour promoter phorbol myristate acetate (PMA). Whereas preincubation with PMA completely eliminated PMA-induced PAI-1 synthesis and secretion in both CCL64 and BSC-1 cells, this treatment had no effect on TGF-beta- and EGF-induced PAI-1 levels. Therefore we conclude that protein kinase C does not mediate the effects of either EGF or TGF-beta on PAI-1 expression. The expression of PAI-1 was decreased by agents increasing intracellular cyclic AMP: (cAMP) cholera toxin, forskolin and dibutyryl cAMP lowered both the basal level and the TGF-beta- and PMA-induced levels of PAI-1 expression. These effects of cAMP-elevating agents and of TGF-beta on PAI-1 protein synthesis were also reflected in changes in TGF-beta-induced PAI-1 gene transcription, as measured by nuclear run-on. These results show that PAI-1 gene expression is sensitive to high levels of intracellular cAMP and that this effect occurs at the transcriptional level. Although increased intracellular cAMP concentrations decrease the absolute level of PAI-1 expression, the ability of TGF-beta and EGF to induce PAI-1 gene expression is unchanged. These results are discussed in relation to the observation that sensitivity to cAMP is a common feature of TGF-beta-regulated genes.
Thalacker
F W
FW
Department of Biochemistry, Iowa State University, Ames 50011.
Nilsen-Hamilton
M
M
D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D015536:Down-Regulation; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D000882:Haplorhini; D006801:Humans; D008907:Mink; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D017395:Plasminogen Activator Inhibitor 1; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate