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TGF-beta repression of Id2 induces apoptosis in gut epithelial cells

Y Cao1, X Liu, W Zhang

  • 1Department of Surgery, University of Texas Health Science Center, Houston, TX 77030, USA. Yanna.Cao@uth.tmc.edu

Oncogene
|January 13, 2009
PubMed

Insights

Transforming growth factor-beta (TGF-beta) induces apoptosis in intestinal cells by repressing inhibitor of differentiation (Id) genes. Hypoxia-inducing factor-1 (HIF-1) is identified as a key mediator in this TGF-beta-induced apoptosis pathway.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Transforming growth factor-beta (TGF-beta) is crucial for epithelial tissue homeostasis, regulating cell cycle arrest, differentiation, and apoptosis.
  • Dysregulation of the TGF-beta signaling pathway is frequently observed in colorectal cancers.
  • Previous studies established Smad3 as a transcription factor mediating TGF-beta-induced apoptosis.

Purpose of the Study:

  • To identify novel TGF-beta/Smad3 target genes involved in apoptosis regulation in rat intestinal epithelial cells (RIE-1).
  • To elucidate the molecular mechanisms downstream of TGF-beta signaling that control apoptosis.

Main Methods:

  • Affymetrix oligonucleotide microarrays were employed to profile gene expression changes induced by TGF-beta.
  • Gene knockdown and overexpression techniques were used to assess the functional roles of identified genes (Id1, Id2, HIF-1).
  • TranSignal Protein/DNA arrays were utilized to identify downstream targets of TGF-beta signaling.

Main Results:

  • TGF-beta was found to repress the expression of the inhibitor of differentiation (Id) gene family.
  • Knockdown of Id1 and Id2 expression promoted apoptosis in RIE-1 cells, while Id2 overexpression inhibited TGF-beta-induced apoptosis.
  • Hypoxia-inducing factor-1 (HIF-1) was identified as a downstream target of TGF-beta, and its activation was blocked by Id2 overexpression.
  • Knockdown of HIF-1 abrogated TGF-beta-induced apoptosis, establishing HIF-1 as a critical mediator.

Conclusions:

  • The inhibitor of differentiation 2 (Id2) acts upstream of hypoxia-inducing factor-1 (HIF-1) in the TGF-beta apoptotic pathway.
  • HIF-1 is identified as a novel mediator downstream of Id2 in TGF-beta-induced apoptosis.
  • These findings provide new insights into the molecular mechanisms underlying TGF-beta-mediated apoptosis in intestinal epithelial cells and its relevance to cancer.

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