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Direct functional interactions between insulin-like growth factor-binding protein-3 and retinoid X receptor-alpha

B Liu1, H Y Lee, S A Weinzimer

  • 1Department of Pediatrics, University of California, Los Angeles, California 90095-1752, USA.

The Journal of Biological Chemistry
|June 30, 2000
PubMed

Insights

Insulin-like growth factor-binding protein 3 (IGFBP-3) interacts with retinoid X receptor-alpha (RXR-alpha) in the nucleus. This interaction is crucial for IGFBP-3 to induce apoptosis, particularly in prostate cancer cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Insulin-like growth factor-binding protein 3 (IGFBP-3) regulates apoptosis independently of IGF.
  • IGFBP-3 has been observed to localize within the cell nucleus.

Purpose of the Study:

  • To identify nuclear binding partners of IGFBP-3.
  • To investigate the role of these interactions in IGFBP-3-mediated apoptosis.

Main Methods:

  • Yeast two-hybrid screening to identify protein interactions.
  • Co-immunoprecipitation and immunofluorescence to confirm nuclear binding.
  • Apoptosis assays in wild-type and knockout cells.
  • Reporter gene assays to assess transcriptional activity.

Main Results:

  • Retinoid X receptor-alpha (RXR-alpha) was identified as an IGFBP-3 binding partner.
  • IGFBP-3 and RXR-alpha physically interact within the nucleus.
  • IGFBP-3-induced apoptosis was abrogated in RXR-alpha-knockout cells.
  • IGFBP-3 enhanced RXR response element activity and inhibited RARE signaling, suggesting modulation of RXR-alpha transcriptional activity.

Conclusions:

  • The interaction between IGFBP-3 and RXR-alpha is essential for IGFBP-3-induced apoptosis.
  • This interaction modulates the transcriptional activity of RXR-alpha.
  • The IGFBP-3 and RXR-alpha complex plays a significant role in regulating apoptosis, with implications for prostate cancer therapy.

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