A novel multi lines analysis tool of Ca2+ dynamics reveals the nonuniformity of Ca2+ propagation.

Extracellular stimuli evoke a robust increase in the concentration of intracellular Ca2+ ([Ca2+]c) throughout the cell to trigger various cellular responses, such as gene expression and apoptosis. This robust expansion of [Ca2+]c is called Ca2+ propagation. To date, it is thought that intracellular second messengers, such as inositol 1,4,5-trisphosphate (IP3) and intracellular Ca2+, and clusters of IP3 receptors (IP3Rs) regulate Ca2+ propagation. However, little is known about how the elevation in the [Ca2+]c spreads throughout the cell, especially in non-polar cell, including HeLa cell. In this study, we developed a novel multi lines analysis tool. This tool revealed that the velocity of Ca2+ propagation was inconstant throughout cell and local concentration of intracellular Ca2+ did not contribute to the velocity of Ca2+ propagation. Our results suggest that intracellular Ca2+ propagation is not merely the result of diffusion of intracellular Ca2+, and that, on the contrary, intracellular Ca2+ propagation seems to be regulated by more complicated processes.