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. Author manuscript; available in PMC: 2018 Jul 26.
Published in final edited form as: Annu Rev Condens Matter Phys. 2017 Dec 8;9:183–205. doi: 10.1146/annurev-conmatphys-033117-054046

Figure 4.

Figure 4

Adaptation measured in Dictyostelium cells (From (68)). A: Snapshots of a cell undergoing a sudden increase in chemoattractant concentration at t = 0 s (visualized in red). Activated Ras is visualized using RBD-GFP, which shows a transient translocation to the membrane. B: The RBD-GFP cytosolic fluorescence intensity, I(t), normalized by the fluorescence intensity before stimulation, as a function of time for different amounts of stimulation. Note that the time for peak response decreases when the stimulus strength increases. C: The RBD-GFP cytosolic fluorescence intensity as a function of stimulus strength shows perfect adaptation. D: Incoherent feedforward network topology consistent with experimental data: chemoattractant binds to receptors R which activate both RasGEF and RasGAP. These two enzymes then activate (GEF) and inactivate (GAP) Ras. E: Experimental results (RBD-GFP dose-response curves for different pretreatment concentrations, plotted as symbols) and the results of the incoherent feedforward network using model parameters obtained by fitting (plotted as lines).