THE ROLE OF IP₃R CLUSTERING IN Ca²⁺ SIGNALING

Abstract

Ca²⁺ is the most important second messenger controlling a variety of intracellular processes by oscillations of the cytosolic Ca²⁺ concentration. These oscillations occur by Ca²⁺ release from the endoplasmic reticulum (ER) into the cytosol through channels and the re-uptake of Ca²⁺ into the ER by pumps. A common channel type present in many cell types is the inositol trisphosphate receptor (IP₃R), which is activated by IP₃ and Ca²⁺ itself leading to Ca²⁺ induced Ca²⁺ release (CICR). We have shown in an experimental study [15], that Ca²⁺ oscillations are sequences of random spikes that occur by wave nucleation. We use here our recently developed model for Ca²⁺ dynamics in 3 dimension to illuminate the role of IP₃R clustering within spatial extended systems.