Figure 8

Dependence of Ca²⁺ oscillation frequency on the ER-Mt distance. Heatmaps of oscillation frequency at two different levels of IP₃ stimulation ([IP₃] = 0.2 µM in (A,B) [IP₃] = 0.7 µM in C,D) as a function of D and either C_IP3R (A,C) or C_MCU (B,D). Oscillation frequency at higher levels of IP₃ (C,D) remained close to ~3 oscillations per minute, showing less dependence on D. At lower levels of IP₃ stimulation (A,B), oscillation frequency was sensitive to variations in D; the frequency decreased as D increased with complete loss of oscillatory activity when D > ~150 nm. However, oscillations that were completely insensitive to variations in D occurred at low stimulation with C_IP3R < ~0.3 (dark red region in lower part of A).