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Updated: May 26, 2026
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Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos
Published on: April 14, 2023
RhoG, Rac1 and Cdc42 cooperation in cell protrusion revealed by multiplexed optogenetics and biosensor imaging
Frederico M Pimenta1, Jaewon Huh2, Christopher M Welch1
1Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 27599.
Biorxiv : the Preprint Server for Biology
|May 25, 2026
Summary
The small GTPase RhoG regulates cell protrusion by activating Rac1, but also independently controls other cell functions. Researchers developed new tools to visualize and manipulate RhoG and Rac1 activity, clarifying their relationship.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The small GTPase Rac1 is crucial for cell protrusion and various cell functions.
- Regulation of Rac1 by guanine nucleotide exchange factors (GEFs) is well-studied, but the role of GTPase RhoG is less understood.
- RhoG activates the ELMO/DOCK180 GEF complex, which interacts with Rac1, but its specific contributions to protrusion remain unclear.
Purpose of the Study:
- To elucidate the specific roles of RhoG in cell protrusion.
- To determine which effects of RhoG on protrusion are mediated by Rac1.
- To develop novel tools for visualizing and manipulating GTPase activity.
Main Methods:
- Development of novel biosensors and optogenetic tools, including photoactivable RhoG (PA-RhoG) and red-shifted biosensors for RhoG and Rac1.
- Simultaneous visualization of RhoG and Rac1 activity.
- Spatio-temporal correlation analysis and causal inference to establish causal relationships.
- Optogenetic activation of RhoG and Rac1 to dissect signaling pathways.
Main Results:
- RhoG and Rac1 activation events were spatio-temporally correlated with each other and with protrusion velocity.
- Causal inference confirmed that RhoG unidirectionally activates Rac1.
- Optogenetic activation revealed that RhoG controls specific protrusion behaviors, some via Rac1 and others independently.
- PA-RhoG activates Rac1 primarily through DOCK180 and can activate Cdc42 independently of Rac1.
Conclusions:
- RhoG plays a dual role in cell protrusion, acting both through Rac1 activation and via independent pathways.
- The developed biosensors and optogenetic tools provide powerful means to study GTPase signaling.
- RhoG's regulation of cell protrusion involves complex crosstalk with Rac1 and potentially other GTPases like Cdc42.
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