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. 2020 Apr 30;9:e54441. doi: 10.7554/eLife.54441

Figure 1. Simulations: Kinetic properties of glutamate indicators/transporters and simulated synaptic responses.

(A) Simulated iGluSnFR activation by 20 ms applications of glutamate (concentration steps varied logarithmically from 1 μM to 30 mM). (B) Comparison of simulated glutamate dose-response curves for iGluSnFR (black), iGluf (blue), iGluu (gold) and EAAT2 (red). Color scheme applies to the entire figure. (C) Simulated equilibrium affinities (KD, left) and deactivation time constants (mean ± SD, n = 10 different [glu] applications, right) for iGlus and EAAT2. (D) Activation of iGlus and EAAT2 by 1 mM glutamate, normalized and superimposed to compare activation and deactivation kinetics. (E) Responses of iGlus to 1 mM glutamate, scaled according to their background fluorescence and change in fluorescence upon activation (i.e., ΔF/F0 ≍ (Fon-Foff)/Foff; see Figure 1—figure supplement 1; Helassa et al., 2018). (F) Schematic diagrams of simulated synaptic structure (top) and surrounding extracellular space (bottom).

Figure 1—source data 1. Characterization of kinetic models.
Steady-state amplitudes of simulated responses to glutamate application (Figure 1B). Calculated Kd values and measure deactivation time constants (Figure 1C). Mean and SD calculated from responses to all glutamate concentrations.

Figure 1.

Figure 1—figure supplement 1. Kinetic models.

Figure 1—figure supplement 1.

(A) Multi-state model of EAAT2 used in the simulations (Bergles et al., 2002). (B) Multi-state models used to simulate iGluSnFR, iGluf and iGluu (Helassa et al., 2018).