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Updated: Dec 30, 2025
10:27
Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
Published on: March 9, 2012
11.2K
Optogenetics reveals Cdc42 local activation by scaffold-mediated positive feedback and Ras GTPase.
Iker Lamas1, Laura Merlini1, Aleksandar Vještica1
1Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
Plos Biology
|January 25, 2020
Summary
Scaffold-mediated positive feedback regulates cell polarization in fission yeast. This mechanism, involving Cdc42 and its guanine nucleotide exchange factor (GEF), ensures robust formation of two active zones for rod-shape development.
Area of Science:
- Cell Biology
- Molecular Biology
- Biophysics
Background:
- Local activity of the small GTPase Cdc42 is crucial for cell polarization.
- Scaffold-mediated positive feedback was previously proposed for budding yeast symmetry breaking.
- Its existence and mechanism in other organisms, like rod-shaped fission yeast, remained unexplored.
Purpose of the Study:
- To investigate scaffold-mediated positive feedback in fission yeast Schizosaccharomyces pombe.
- To determine the role of the scaffold protein Scd2 and the guanine nucleotide exchange factor (GEF) Scd1 in Cdc42 polarization.
- To explore rewiring positive feedback mechanisms and the involvement of Ras1.
Main Methods:
- Utilized the CRY2-CIB1 optogenetic system for light-dependent protein recruitment.
- Performed optogenetic recruitment of constitutively active Cdc42 to the plasma membrane.
- Investigated the function of Scd2 and engineered interactions between GEF and Cdc42 effector Pak1.
- Analyzed the role of small GTPase Ras1 in GEF localization and activity.
Main Results:
- Directly demonstrated positive feedback through optogenetic recruitment of active Cdc42, Scd1, and endogenous Cdc42, dependent on Scd2.
- Showed Scd2 is dispensable when positive feedback is rewired via GEF-Pak1 interaction.
- Observed that rewired feedback confers viability and allows formation of two Cdc42 zones even without essential activators.
- Revealed Ras1's role in localizing and activating Scd1, potentiating positive feedback.
Conclusions:
- Scaffold-mediated positive feedback, gated by Ras activity, confers robust polarization for rod-shape formation in fission yeast.
- Positive feedback mechanisms can be rewired to maintain cell polarization under challenging conditions.
- Cdc42 activity and polarization are tightly regulated by scaffold proteins and upstream activators like Ras1.
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