Intra-Cluster Percolation of Calcium Signals

G SOLOVEY

Seminario; NJIT Mathematical Biology Seminar; 2010

Calcium signals are involved in a large variety of physiological processes. Their versatility relies on the diversity of spatio-temporal behaviors that the calcium concentration can display. Calcium entry through inositol 1,4,5-trisphosphate (IP3) receptors (IP3R’s) is a key component of the calcium signaling toolkit. IP3R’s are usually organized in clusters on the membrane of the endoplasmic reticulum and their spatial distribution has important effects on the resulting signal. Recent high resolution observations of calcium puffs offer a window to study intra-cluster organization. The experiments give the distribution of the number of IP3R’s that open during each puff without much processing. In this talk, I will present a simple model with which we interpret the experimental distribution in terms of two stochastic processes: IP3 binding and unbinding and calcium mediated inter-channel coupling. Depending on the parameters of the system, the distribution may be dominated by one or the other process. The transition between both extreme cases is similar to a percolation process. The approach allows us to infer properties of the interactions among the channels of the cluster from statistical information on their emergent collective behavior.