Figure 4. The rate of Ca²⁺ entry into mitochondria alters cytosolic Ca²⁺ oscillations.

(A) Relationship between the frequency of oscillations and the rate constant of the MCU. The rate constant of the NCX is the default value (black curve, V_NCX = 0.35 μM.s⁻¹) or is increased (red curve, V_NCX = 1 μM.s⁻¹). (B) Effect of the rate constant of the MCU on cytosolic Ca²⁺ oscillations, as predicted by the model. The black curve shows oscillations for the default value (V_MCU = 0.0006 μM.s⁻¹) given in Table 1, while the red curve shows oscillations obtained when V_MCU = 0. (C,D) Measurement of Ca²⁺ variations in control (C) or MCU-silenced HeLa cells (D). Cells loaded with Fluo4 were perfused with 3 μM histamine for the time shown by the black line. Experiments are representative of more than five trials. See also Supplementary Fig. S4.