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Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay
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Nuclear insulin receptor substrate 1 interacts with estrogen receptor alpha at ERE promoters

Catia Morelli1, Cecilia Garofalo, Diego Sisci

  • 1Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Oncogene
|August 20, 2004
PubMed

Insights

Nuclear insulin receptor substrate 1 (IRS-1) translocates to the nucleus in breast cancer cells, interacting with estrogen receptor alpha (ERalpha) and potentially modulating its transcriptional activity.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Oncology

Background:

  • Insulin receptor substrate 1 (IRS-1) is a key signaling molecule for insulin and IGF-I receptors.
  • Emerging evidence suggests IRS-1 functions within the nuclear compartment, beyond its cytoplasmic role.
  • The nuclear function of IRS-1 in breast cancer remains unexplored.

Purpose of the Study:

  • To investigate the role of nuclear IRS-1 in estrogen receptor alpha (ERalpha)-positive breast cancer cells.
  • To determine if IRS-1 interacts with ERalpha and influences its transcriptional activity.

Main Methods:

  • Treatment of MCF-7 cells with 17-beta-estradiol (E2) and an antiestrogen (ICI 182,780).
  • Analysis of IRS-1 nuclear translocation, colocalization, and co-precipitation with ERalpha.
  • Chromatin immunoprecipitation assays to assess promoter recruitment.
  • Reporter gene assays to evaluate ERalpha transcriptional activity.

Main Results:

  • 17-beta-estradiol (E2) induced nuclear translocation of IRS-1 in ERalpha-positive MCF-7 cells.
  • Nuclear IRS-1 colocalized and co-precipitated with ERalpha, forming a complex recruited to the pS2 gene promoter.
  • IRS-1 interaction with the pS2 promoter was ERalpha-dependent.
  • Nuclear IRS-1 inhibited ERalpha transcriptional activity on E2-sensitive promoters.

Conclusions:

  • Nuclear translocation of IRS-1 is regulated by E2 in ERalpha-positive breast cancer cells.
  • IRS-1 forms a complex with ERalpha that is recruited to target gene promoters.
  • This IRS-1:ERalpha interaction may play a role in regulating ERalpha-mediated transcription in breast cancer.

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