Protease nexin-1, a thrombin inhibitor, is regulated by interleukin-1 and dexamethasone in normal human fibroblasts

J Biol Chem. 1993 Sep 5;268(25):18966-74.

Abstract

Thrombin participates in several regulatory events following injury as a result of its effects on blood coagulation and cell migration, proliferation, and differentiation. Protease nexin-1 (PN-1) is a potent thrombin inhibitor in the extracellular environment. Since injury-related factors are known to regulate the synthesis and secretion of PN-1, the inhibitor may serve to modulate the actions of thrombin during injury. Here we report the molecular mechanisms that underlie this regulation. In normal human fibroblasts, interleukin-1 (IL-1) beta stimulated the synthesis and secretion of PN-1. The stimulation correlated with an increase in steady-state levels of PN-1 mRNA. Treatment of cells with both cycloheximide and IL-1 reduced the levels of PN-1 mRNA. Nuclear run-on assays indicated that IL-1 modestly increased the rate of PN-1 transcription. However, experiments with actinomycin D demonstrated that IL-1 significantly increased the half-life of the PN-1 mRNA. In contrast, dexamethasone (DXM) repressed the synthesis and secretion of PN-1 from fibroblasts. This effect correlated with a decrease in PN-1 mRNA. A sustained decrease in PN-1 mRNA was also seen when cells were treated with cycloheximide and DXM. In nuclear run-on assays, DXM functioned as a transcriptional repressor of PN-1 synthesis. Treatment of cells with actinomycin D showed that DXM did not affect mRNA stability. Thus, our experiments demonstrate that IL-1 and DXM, which function biologically in different fashions, regulate the synthesis of PN-1 by separate molecular mechanisms. While DXM directly regulates PN-1 at the level of transcription, IL-1 in the presence of ongoing protein synthesis regulates PN-1 production predominantly in a post-transcriptional fashion by increasing the half-life of the PN-1 mRNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amyloid beta-Protein Precursor
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Carrier Proteins / pharmacology
  • Cycloheximide / pharmacology
  • Cytokines / pharmacology
  • Dactinomycin / pharmacology
  • Dexamethasone / pharmacology*
  • Drug Stability
  • Extracellular Matrix / metabolism
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism*
  • Gene Expression Regulation*
  • Humans
  • Interleukin-1 / pharmacology*
  • Protease Nexins
  • RNA, Messenger / metabolism
  • Receptors, Cell Surface
  • Serpin E2
  • Thrombin / antagonists & inhibitors*
  • Thrombin / metabolism
  • Transcription, Genetic / drug effects

Substances

  • Amyloid beta-Protein Precursor
  • Carrier Proteins
  • Cytokines
  • Interleukin-1
  • Protease Nexins
  • RNA, Messenger
  • Receptors, Cell Surface
  • SERPINE2 protein, human
  • Serpin E2
  • Dactinomycin
  • Dexamethasone
  • Cycloheximide
  • Thrombin