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Long form of cellular FLICE-inhibitory protein interacts with Daxx and prevents Fas-induced JNK activation

Young-Youl Kim1, Bum-Joon Park, Gill-Ju Seo

  • 1National Genome Research Institute, National Institute of Health in Korea (KNIH) Nokbun-Dong 5, Eunpyung-Gu, 122-701, Seoul, Republic of Korea

Biochemical and Biophysical Research Communications
|November 26, 2003
PubMed

Insights

Cellular FLICE-inhibitory protein long form (c-FLIP(L)) prevents Fas-induced apoptosis by binding Daxx, inhibiting JNK activation and cell death. This explains c-FLIP(L)

Area of Science:

  • Cellular biology
  • Molecular oncology
  • Apoptosis signaling

Background:

  • Fas-induced apoptosis is crucial for eliminating abnormal cells.
  • Cancer cells often develop resistance to apoptosis.
  • Cellular FLICE-inhibitory protein (c-FLIP) is overexpressed in human cancers, conferring resistance.

Purpose of the Study:

  • To elucidate the functional differences between c-FLIP isoforms, c-FLIP(L) and c-FLIP(S).
  • To investigate the mechanism by which c-FLIP isoforms confer resistance to Fas-induced apoptosis.
  • To identify novel interactions of c-FLIP with Fas signaling adaptors.

Main Methods:

  • Co-immunoprecipitation assays to detect protein-protein interactions.
  • Cell viability assays to assess apoptosis.
  • Western blotting to analyze JNK pathway activation.
  • Overexpression studies of c-FLIP isoforms in cancer cell lines.

Main Results:

  • c-FLIP(L), but not c-FLIP(S), physically binds to Daxx via specific domains.
  • Cells with low c-FLIP(L) levels are sensitive to Fas-induced cell death and JNK activation.
  • Overexpression of c-FLIP(L) confers resistance to Fas-induced apoptosis and JNK activation, while c-FLIP(S) does not.
  • The interaction between c-FLIP(L) and Daxx inhibits JNK activation by disrupting the Daxx-Fas interaction.

Conclusions:

  • c-FLIP(L) inhibits Fas-induced apoptosis through a novel mechanism involving Daxx.
  • This interaction prevents JNK activation and subsequent cell death.
  • c-FLIP(L) acts on both FADD- and Daxx-mediated pathways for complete inhibition of Fas signaling.
  • The findings explain the greater abundance and efficacy of c-FLIP(L) compared to c-FLIP(S) in cancer resistance.

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