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Proteasome affects the expression of aryl hydrocarbon receptor-regulated proteins

Takumi Ishida1, Masayo Kawakami, Hiroko Baba

  • 1Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.

Environmental Toxicology and Pharmacology
|July 28, 2011
PubMed

Insights

Proteasome inhibition, using N-acetyl-leucyl-leucyl-norleucinal (ALLN), reduces aryl hydrocarbon receptor (AhR)-regulated protein expression. This effect was observed in T47D breast tumor cells, impacting reporter gene activity and ethoxyresorufin O-deethylase (EROD) activity.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Pharmacology

Background:

  • The aryl hydrocarbon receptor (AhR) is a key regulator of xenobiotic metabolism and cellular responses.
  • Proteasomes are crucial cellular machinery responsible for protein degradation.
  • Understanding the interplay between proteasome activity and AhR signaling is important for drug development and toxicology.

Purpose of the Study:

  • To investigate the impact of proteasome inhibition on AhR-mediated gene and protein expression.
  • To determine if proteasome inhibitors affect AhR-regulated enzyme activity and protein levels.

Main Methods:

  • Utilized T47D breast tumor cells for experiments.
  • Employed a luciferase reporter gene assay with a xenobiotic responsive element.
  • Measured ethoxyresorufin O-deethylase (EROD) activity.
  • Assessed mRNA expression of CYP1A1 and CYP1B1.
  • Used proteasome inhibitors N-acetyl-leucyl-leucyl-norleucinal (ALLN) and lactacystin, and cysteine protease inhibitor leupeptin.

Main Results:

  • Proteasome inhibition with ALLN significantly reduced AhR ligand-induced reporter gene expression.
  • ALLN also suppressed 3-methylcholanthrene (3MC)-induced ethoxyresorufin O-deethylase (EROD) activity.
  • Conversely, ALLN did not affect the induced expression of CYP1A1 and CYP1B1 mRNAs.
  • Lactacystin showed a similar suppressive effect on EROD activity, while leupeptin did not.

Conclusions:

  • Proteasome inhibition leads to decreased expression of proteins regulated by the aryl hydrocarbon receptor (AhR).
  • The findings suggest a role for the proteasome in the post-transcriptional regulation of AhR-mediated protein production.

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