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Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
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Phosphorylation-dependent inhibition of Cdc42 GEF Gef1 by 14-3-3 protein Rad24 spatially regulates Cdc42 GTPase

Maitreyi Das1, Illyce Nuñez1, Marbelys Rodriguez1

  • 1Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.

Molecular Biology of the Cell
|August 7, 2015
PubMed

Insights

The 14-3-3 protein Rad24 limits the availability of Gef1, a Cdc42 guanine exchange factor (GEF), to control cell polarity. This regulation is crucial for cell shape and polarization in fission yeast.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Active Cdc42 GTPase regulates cell polarity in fission yeast, exhibiting anticorrelated oscillations at cell tips.
  • Anticorrelation suggests competition for active Cdc42 or its effectors, indicating a regulatory mechanism is at play.

Purpose of the Study:

  • To elucidate the role of the 14-3-3 protein Rad24 in modulating Cdc42 GTPase activity and cell polarity.
  • To investigate how Rad24-Gef1 interaction influences Gef1 availability and subsequent Cdc42 activation dynamics.

Main Methods:

  • Investigated the interaction between Rad24 and Gef1 using biochemical and cell biological approaches.
  • Analyzed the effects of modulating Rad24-Gef1 interaction on Cdc42 activation, cell growth, and cell shape in fission yeast.

Main Results:

  • Rad24 associates with Gef1, limiting its availability and promoting Cdc42 activation, with this interaction mediated by Gef1 phosphorylation by Orb6.
  • Loss of Rad24-Gef1 interaction led to increased Gef1 localization, enhanced Cdc42 activation, and reduced anticorrelation of Cdc42 oscillations.
  • Increased Cdc42 activation by Gef1 promoted precocious bipolar growth and altered cell morphology, affecting cell diameter and tip curvature.

Conclusions:

  • The 14-3-3 protein Rad24 spatially controls Cdc42 GTPase activity by modulating Gef1 availability, impacting cell polarization and cell shape emergence.
  • This mechanism, involving Rad24 and Gef1 (a homolog of mammalian DNMBP/TUBA), provides spatial control over cell growth and polarity.

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