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Transforming growth factor beta-dependent sequential activation of Smad, Bim, and caspase-9 mediates physiological

Masatoshi Ohgushi1, Shunsuke Kuroki, Hiroshi Fukamachi

  • 1Graduate School of Biostudies, Kyoto University, SCRB/Building G, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.

Molecular and Cellular Biology
|November 2, 2005
PubMed

Insights

Transforming growth factor beta (TGF-beta) triggers gastric epithelial cell loss via apoptosis. This process involves Smad signaling, Bim, and caspase-9, crucial for maintaining stomach homeostasis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Gastroenterology

Background:

  • Transforming growth factor beta (TGF-beta) is vital for gastric epithelium homeostasis.
  • TGF-beta signaling regulates physiological apoptosis in gastric cells, but the mechanism remains unclear.

Purpose of the Study:

  • To elucidate the molecular mechanism of TGF-beta-induced apoptosis in human gastric epithelial cells.
  • To investigate the roles of Smad signaling, Bcl-2 family proteins, and caspases in this process.

Main Methods:

  • Utilized SNU16 human gastric epithelial cell line for in vitro studies.
  • Analyzed gene and protein expression, including Smad7, Bcl-X(L), and Bim.
  • Employed RNA interference and knockout mouse models (Bim and caspase-9).

Main Results:

  • Smad7 and Bcl-X(L) expression inhibited TGF-beta-induced apoptosis, highlighting Smad pathway activation and mitochondrial dysfunction.
  • TGF-beta treatment increased Bim binding to Bcl-X(L) in a Smad-dependent manner.
  • Bim knockdown reduced sensitivity to TGF-beta-induced apoptosis.
  • Bim and caspase-9 knockout mice exhibited gastric epithelial abnormalities and defective physiological apoptosis.

Conclusions:

  • TGF-beta induces gastric epithelial cell apoptosis through the Smad signaling pathway.
  • Bim and caspase-9 are critical mediators of TGF-beta-induced physiological apoptosis in the gastric epithelium.
  • This study reveals a novel mechanism for maintaining gastric homeostasis via TGF-beta-mediated apoptosis.

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