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Cdc42 and Rac1 regulate the interaction of IQGAP1 with beta-catenin

M Fukata1, S Kuroda, M Nakagawa

  • 1Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan.

The Journal of Biological Chemistry
|September 3, 1999
PubMed

Insights

Cdc42 and Rac1 regulate IQGAP1 by inhibiting its interaction with beta-catenin. This action stabilizes E-cadherin-mediated cell adhesion, impacting cell-cell interactions.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • IQGAP1 is a protein that interacts with beta-catenin and negatively regulates E-cadherin-mediated cell-cell adhesion.
  • This regulation occurs through the dissociation of alpha-catenin from the cadherin-catenin complex.
  • The small GTPases Cdc42 and Rac1 are known targets that influence IQGAP1 function.

Purpose of the Study:

  • To investigate the regulatory mechanisms by which Cdc42 and Rac1 control IQGAP1 activity.
  • To elucidate the specific interactions between IQGAP1, beta-catenin, and alpha-catenin.
  • To understand the role of Cdc42 and Rac1 in modulating E-cadherin-mediated cell adhesion.

Main Methods:

  • In vitro binding assays to study protein-protein interactions.
  • Coexpression studies in L cells (EL cells) to assess functional consequences.
  • Use of dominant active and dominant negative forms of Cdc42 and Rac1.

Main Results:

  • IQGAP1 interacts with the N-terminal region of beta-catenin, disrupting the beta-catenin-alpha-catenin complex.
  • Activated Cdc42 and Rac1 (GTPgammaS-bound) inhibit IQGAP1 binding to beta-catenin.
  • Overexpression of dominant active Cdc42 prevents IQGAP1-induced dissociation of alpha-catenin.
  • Inhibition of Cdc42 or Rac1 reduces E-cadherin-mediated cell adhesion.

Conclusions:

  • Cdc42 and Rac1 negatively regulate IQGAP1 function by preventing its interaction with beta-catenin.
  • This regulation leads to the stabilization of the cadherin-catenin complex.
  • The findings clarify a key mechanism controlling E-cadherin-mediated cell adhesion.

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