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Suppression of TGF-beta signaling by conophylline via upregulation of c-Jun expression

S Atsumi1, A Nagasawa, T Koyano

  • 1Microbial Chemistry Research Center, 3-14-23 Kamioosaki, Shinagawa-ku, Tokyo 141-0021, Japan. atsumi@bikaken.or.jp

Cellular and Molecular Life Sciences : CMLS
|November 20, 2003
PubMed

Insights

Conophylline, a vinca alkaloid, inhibits transforming growth factor-beta (TGF-β) functions by upregulating c-Jun. This modulation affects downstream transcription factors, suppressing TGF-β-induced promoter activity.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Pharmacology

Background:

  • Transforming growth factor-beta (TGF-β) signaling pathways are crucial in cellular processes.
  • Vinca alkaloids, like conophylline, are known for their biological activities.
  • Understanding TGF-β inhibition mechanisms is vital for therapeutic development.

Purpose of the Study:

  • To elucidate the mechanism by which conophylline inhibits TGF-β-induced promoter activity.
  • To investigate the role of downstream transcriptional factors in conophylline's inhibitory action.
  • To determine if conophylline affects Smad2 nuclear translocation or its interactions.

Main Methods:

  • Screening for TGF-β inhibitors.
  • Utilizing mink lung cells for mechanistic studies.
  • Assessing Smad2 nuclear translocation.
  • Analyzing protein-protein interactions (Smad2 complex with p300 and TGIF).
  • Measuring promoter activity and gene expression (c-Jun).

Main Results:

  • Conophylline inhibited TGF-β-induced apoptosis in rat hepatoma cells and promoter activity in mink lung cells.
  • Conophylline did not inhibit Smad2 nuclear translocation.
  • Conophylline increased c-Jun expression, attenuated Smad2-p300 interaction, and enhanced Smad2-TGIF interaction.
  • Overexpression of c-Jun mimicked conophylline's effects on TGF-β signaling.

Conclusions:

  • Conophylline inhibits TGF-β-induced promoter activity by upregulating c-Jun expression.
  • The mechanism involves modulating interactions of the Smad2 complex with downstream factors like TGIF.
  • Conophylline's effects are mediated through c-Jun-dependent suppression of TGF-β signaling.

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