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Ionizing radiation suppresses FAP-1 mRNA level in A549 cells via p53 activation

Toru Yamada1, Muneharu Maruyama, Tadashi Fujita

  • 1The First Department of Internal Medicine, Faculty of Medicine, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan.

FEBS Letters
|July 18, 2006
PubMed

Insights

Ionizing radiation (IR) upregulates cell surface Fas. This study reveals IR down-modulates Fas-associated phosphatase-1 (FAP-1) via p53 activation, suggesting a novel pathway for Fas regulation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Radiation Oncology

Background:

  • Ionizing radiation (IR) is known to increase cell surface Fas expression, a key mediator of apoptosis.
  • The precise molecular mechanisms linking p53 activation to Fas upregulation following IR are not fully understood.
  • Fas-associated phosphatase-1 (FAP-1) has been identified as a negative regulator of cell surface Fas expression.

Purpose of the Study:

  • To investigate the role of FAP-1 in the p53-mediated upregulation of cell surface Fas after ionizing radiation.
  • To elucidate the signaling pathway connecting p53 activation to Fas expression modulation by IR.

Main Methods:

  • Quantitative analysis of FAP-1 mRNA expression in A549 cells following ionizing radiation exposure.
  • Assessment of FAP-1 mRNA levels after pretreatment with pifithrin alpha, a p53 inhibitor.

Main Results:

  • Ionizing radiation significantly inhibited FAP-1 mRNA expression in A549 cells.
  • Pretreatment with the p53 inhibitor pifithrin alpha abrogated the IR-induced downregulation of FAP-1 mRNA.
  • These findings indicate that p53 activation is responsible for the observed decrease in FAP-1 expression.

Conclusions:

  • IR-induced p53 activation leads to the downregulation of FAP-1.
  • The down-modulation of FAP-1 by p53 likely contributes to the upregulation of cell surface Fas expression following ionizing radiation.
  • This study proposes a novel signaling axis (IR → p53 → FAP-1 ↓ → Fas ↑) in radiation-induced apoptosis.

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