Reconstitution of Ras-PI3Kγ membrane communication and feedback using light-induced signaling inputs
Sophia Doerr1,2, Andrés Olavarrieta Colasurdo1,3,4, Scott D Hansen5,6
1Institute of Molecular Biology, University of Oregon, Eugene, OR, USA.
Nature Communications
|July 16, 2026
Summary
Small GTPase Ras and PI3Kγ signaling modules form excitable networks. Positive feedback drives sustained activity waves, crucial for cell signaling dynamics under inhibition.
Area of Science:
- Cellular signaling and membrane biophysics.
- Biochemistry and molecular dynamics.
- Systems biology and network emergence.
Background:
- Small GTPases and phosphoinositide lipids are key regulators of cell signaling.
- Feedback loops between these molecules generate complex cellular behaviors like excitability and polarization.
- Understanding these dynamics is crucial for deciphering cellular functions.
Purpose of the Study:
- To reconstitute and analyze the signaling module of Ras GTPase and PI3Kγ-mediated PIP3 production on supported membranes.
- To investigate the role of positive feedback in regulating the spatiotemporal dynamics of this signaling module.
- To elucidate how activation thresholds, membrane diffusion, and feedback architecture influence signaling behavior.
Main Methods:
- Reconstitution of the Ras-PI3Kγ signaling module using purified proteins on supported membranes.
- Utilizing light-induced membrane recruitment for rapid perturbation of steady-state conditions.
- Observing spatiotemporal responses of Ras(GTP) and PIP3 to analyze module dynamics.
Main Results:
- The Ras-PI3Kγ module alone shows transient and reversible activation due to global inhibition.
- Introduction of GEF-mediated positive feedback leads to sustained threshold crossing and local amplification.
- A traveling, bistable wave of Ras(GTP) and PIP3 activity, characteristic of excitable networks, was observed.
Conclusions:
- Positive feedback is essential for sustained signaling and amplification in the Ras-PI3Kγ module.
- The dynamics of Ras-PI3Kγ signaling are governed by activation thresholds, membrane diffusion, and feedback circuit design.
- This study provides insights into the emergent properties of membrane signaling networks.
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