Figure 9.

Diagram of the mechanism of IP₃-induced modulation of cytosolic Ca²⁺ oscillations: an integrated control of the filling state of the ER/SR and mitochondria. IP₃-induced Ca²⁺ release from the ER generates a high Ca²⁺ concentration in the vicinity of mitochondria. Thereby, mitochondria take up Ca²⁺ released by the IP₃-sensitive ER and trap part of the Ca²⁺cycling from and into the SR through the uniporter. Alternatively, the SR may be in privileged communication with and may provide the ER with Ca²⁺ to refill after mitochondrial Ca²⁺ sequestration. In both situations, the SR is partially Ca²⁺depleted, and in turn, cytosolic Ca²⁺ oscillations are slowed or stopped.