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CIS1 interacts with the Y532 of the prolactin receptor and suppresses prolactin-dependent STAT5 activation

Takaho Endo1, Atsuo Sasaki, Mayu Minoguchi

  • 1Institute of Life Science, Kurume University, Aikawa-machi 2432-3, Kurume 839-0861.

Journal of Biochemistry
|May 23, 2003
PubMed

Insights

Cytokine-Inducible SH2 domain-containing protein-1 (CIS1) suppresses prolactin (PRL) signaling by binding to the PRL receptor in a JAK2-dependent manner. This interaction, specifically at phosphorylated Y532, suggests a novel mechanism beyond simple competition with STAT5.

Area of Science:

  • Cellular signaling pathways
  • Molecular biology
  • Endocrinology

Background:

  • Prolactin (PRL) signaling is mediated by the PRL receptor and JAK2 kinase, leading to STAT5 activation.
  • Cytokine-Inducible SH2 domain-containing protein-1 (CIS1) is a STAT5-dependent gene that negatively regulates PRL-induced STAT5 activation.
  • Understanding the precise mechanism of CIS1-mediated suppression is crucial for deciphering PRL signaling.

Purpose of the Study:

  • To investigate the interaction between CIS1 and the PRL receptor.
  • To elucidate the role of JAK2 kinase in the CIS1-PRL receptor interaction.
  • To identify the specific binding site of CIS1 on the PRL receptor.

Main Methods:

  • Development and application of a yeast tri-hybrid system, a modification of the yeast two-hybrid system.
  • Expression of CIS1 and PRL receptor domains fused to yeast transcription factors.
  • Analysis of protein-protein interactions in the presence and absence of JAK2 kinase domain.

Main Results:

  • CIS1 binds to the cytoplasmic domain of the PRL receptor in a JAK2-dependent manner.
  • Phosphorylated Y532 of the murine PRL receptor was identified as the specific binding site for CIS1.
  • CIS1 binding to Y532, which is not essential for STAT5 activation, suggests a non-competitive inhibitory mechanism.

Conclusions:

  • CIS1 interacts with the PRL receptor at phosphorylated Y532, requiring JAK2 activity.
  • The suppression of STAT5 activation by CIS1 is likely mediated by a direct modification of the PRL receptor upon CIS1 binding, rather than simple competition with STAT5.

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