Developmental regulation of the human cathepsin G gene in myelomonocytic cells

J Biol Chem. 1990 Jan 25;265(3):1524-30.

Abstract

Cathepsin G is a neutral serine protease that is found in the azurophil granules of neutrophils and monocytes. Previous experiments had demonstrated that cathepsin G is actively produced by the promonocytic U937 cell line, and that 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of these cells toward macrophages resulted in a reduction of cathepsin G activity. In this study, we have analyzed the mechanism of this TPA-induced down-regulatory event. Using in situ hybridization techniques, we demonstrated that cathepsin G mRNA is detectable only at the promyelocytic stage of myeloid development. Using U937 promonocytic cells as a model, we demonstrated; 1) cathepsin G protein levels decline in TPA-treated cells; 2) this decline was due to a nearly complete loss of cathepsin G mRNA in cells treated with TPA for 24 h; and 3) the rate of cathepsin G mRNA loss with TPA treatment was similar to that with actinomycin D. These results suggested that cathepsin G transcription was down-regulated within several hours of TPA addition. This was directly tested by performing nuclear run-off assays of TPA-treated U937 cells; cathepsin G transcription was shown to be strand-specific, and declined within 4 h of TPA addition. Cathepsin G transcription was essentially undetectable 8 or more hours after TPA treatment, suggesting that down-regulation is predominantly transcriptional. Cycloheximide treatment of U937 cells resulted in a partial block of TPA-mediated cathepsin G down-regulation, indicating that continuous protein synthesis is required for down-regulation to occur. A newly synthesized protein or proteins may therefore be required for the transcriptional down-regulation of cathepsin G during the normal development of promyelocytes or promonocytes.

Publication types

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

MeSH terms

  • Cathepsin G
  • Cathepsins / genetics*
  • Cathepsins / metabolism
  • Cell Differentiation / drug effects
  • Cell Line
  • Cycloheximide / pharmacology
  • Dactinomycin / pharmacology
  • Down-Regulation / drug effects
  • Gene Expression Regulation / drug effects
  • Humans
  • Monocytes / physiology*
  • Nucleic Acid Hybridization
  • RNA, Messenger / genetics
  • Serine Endopeptidases
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription, Genetic / drug effects

Substances

  • RNA, Messenger
  • Dactinomycin
  • Cycloheximide
  • Cathepsins
  • Serine Endopeptidases
  • CTSG protein, human
  • Cathepsin G
  • Tetradecanoylphorbol Acetate