Inferring single calcium channel properties from global calcium signals

G SOLOVEY; D FRAIMAN; B PANDO; S P DAWSON

Bariloche, Argentina

Workshop; Latin American Workshop on Nonlinear Phenomena; 2005

Calcium signals are key factors on the regulation of a large variety of  physiological processes. In eukaryotic cells, calcium is kept at high  concentrations inside intracellular stores and released to the cytosol through  specific ligand gated calcium channels, such as the IP3 receptor. The calcium  liberation of from a single IP3 receptor channel produces a relatively small  signal (blip), but when several channels within a cluster open  synchronously, larger signals are produced (puffs). In this work we are  interested in inferring single channel properties from  experimental records of calcium puffs observed in Xenopus oocytes using fluorescent indicators and  optical techniques. To this end, we analyze the relationship between the amplitude and duration of the puffs observed in the experiments. Using a stochastic  IP3-receptor model together with a simplified diffusion scheme for calcium,  we extract the main features of the single channel mean open time, in particular,  its dependence on the cytosolic calcium concentration.