Post‐Transcriptional regulationa of collagenase and stromelysin gene expression by epidermal growth factor and dexamethasone in cultured human fibroblasts

Publisher Website
Google Scholar
Abstract
Epidermal growth factor (EGF) is a ubiquitous fibroblast mitogen which also stimulates the synthesis of the extracellular matrix degrading metalloproteinases, collagenase, and stromelysin. Using primary cultures of human skin fiibroblassts, we show that these metalloproteinase mRNAs are coordinately up‐regrated by EGF; and that dexamethasone, a potent inhibitor of collagenase and stromelysin syntehse, cordinately down‐regulates these EGF‐induced mRNAs. Nuclear run‐on assays showed that EGF increased trasncription of collagenase and stromelysin ∼ 2‐fold over the untreated control, while repression by dexamethasone was difficult to detect. However, steady state mRNA levels were induced ∼ 10‐fold by EGF and co‐treatment with dexamethasone decreased them to below control levels, suggesting modulation of mRNA stability. Thus, we measured the half‐life of these mRNAs using “pulse‐chase” methodology. Typically, the half‐life of EGF‐induced collagenase and stromelysin mRNAs was ∼ 30 h, and co‐treatment inhibitor DRB stabilized EGF‐induced metalloproteinase mRNAs by 30–50%. Additionally, we found that the transcirption inhibitor DRB stabilitzed EGF‐induced metalloproteinase mRNAs, suggesting an mRNA degradation pathway which requires transcription. Thus our data demonstrate that collagenase and stromelysin are coordinately regulated by EGF and by dexamethasone, primarily at the level of metalloproteinase mRNA stability.