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IQGAP1 is a component of Cdc42 signaling to the cytoskeleton

Jennifer M Swart-Mataraza1, Zhigang Li, David B Sacks

  • 1Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.

The Journal of Biological Chemistry
|April 12, 2002
PubMed

Insights

IQGAP1 enhances active Cdc42 signaling, promoting actin microspike formation. A mutant IQGAP1 (IQGAP1deltaGRD) inhibits Cdc42, altering cell morphology and blocking downstream effects.

Area of Science:

  • Cellular biology
  • Molecular signaling
  • Cytoskeletal dynamics

Background:

  • IQGAP1 is a scaffold protein interacting with actin, calmodulin, E-cadherin, and Cdc42.
  • Understanding IQGAP1's in vivo function is crucial for deciphering its role in cellular processes.

Purpose of the Study:

  • To investigate the in vivo function of IQGAP1 in mammalian cells.
  • To elucidate the mechanism by which IQGAP1 influences Cdc42 signaling and cytoskeletal organization.

Main Methods:

  • Overexpression of wild-type IQGAP1 and a mutant IQGAP1 (IQGAP1deltaGRD) in mammalian cells.
  • Assays to measure GTP-bound Cdc42 levels, Cdc42 activation, membrane translocation, and filopodia formation.
  • In vitro analysis of IQGAP1's effect on Cdc42 GTPase activity.

Main Results:

  • IQGAP1 overexpression increased active, GTP-bound Cdc42 and actin microspikes.
  • IQGAP1deltaGRD decreased GTP-bound Cdc42, blocked Cdc42 activation by bradykinin, and altered cell morphology.
  • IQGAP1deltaGRD enhanced Cdc42's intrinsic GTPase activity, leading to increased inactive, GDP-bound Cdc42.

Conclusions:

  • IQGAP1 plays a critical role in transducing Cdc42 signals to the cytoskeleton.
  • IQGAP1 acts as a positive regulator of Cdc42 activity, influencing actin dynamics and cell shape.
  • The GAP-related domain of IQGAP1 is essential for its function in regulating Cdc42 signaling.

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