Neurite extensions in chromaffin cells: study of the influence of the cytoskeletal structure on calcium dynamics and secretion

Abstract

The extension of neurites by bovine chromaffin cells in culture represents an opportunity to analyse the factors contributing to shape secretion from a round endocrine to a polarized neuronal model. Neurite-emitting chromaffin cells indeed present a different cytoskeletal organization characterized by smaller cytoskeletal cages when compared to round cells and also show a higher density of P/Q-type calcium channels at the neurite tips. Furthermore, these cells present faster and more transient secretory kinetics at the neurite processes when compared with the secretory activity found in round cells. These results were taken into account when proposing a stochastic mathematical model to analyse the impact of different factors in intracellular calcium elevations and the resulting secretory kinetics. Thus, our modelling studies predict that the accumulation of calcium channels at the neurite tips is a major cause of accelerated secretory kinetics, whereas reducing the space for calcium diffusion consequence of smaller cytoskeletal cages enhances the sensitivity of secretion to lower calcium concentrations when assuming a porosity factor for calcium crossing F-actin structures.