Stochastic properties of Ca2+ release of inositol 1,4,5-trisphosphate receptor clusters

Intracellular Ca2+ release is controlled by inositol 1,4,5-trisphosphate (IP3) receptors or ryanodine receptors. These receptors are typically distributed in clusters with several or tens of channels. The random opening and closing of these channels introduces stochasticity into the elementary calcium release mechanism. Stochastic release events have been experimentally observed in a variety of cell types and have been termed sparks and puffs. We put forward a stochastic version of the Li-Rinzel model (the deactivation binding process is described by a Markovian scheme) and a computationally more efficient Langevin approach to model the stochastic Ca2+ oscillation of single clusters. Statistical properties such as Ca2+ puff amplitudes, lifetimes, and interpuff intervals are studied with both models and compared with experimental observations. For clusters with tens of channels, a simply decaying amplitude distribution is typically observed at low IP3 concentration, while a single peak distribution appears at high IP3 concentration.