Physiological manipulation of cellular activity tunes protein and ultrastructural profiles in a neuroendocrine cell.

To study in vivo the dynamics of the biosynthetic and secretory processes in a neuroendocrine cell, we use the proopiomelanocortin-producing intermediate pituitary melanotrope cells of Xenopus laevis. The activity of these cells can be simply manipulated by adapting the animal to a white or a black background, resulting in inactive and hyperactive cells respectively. Here, we applied differential display proteomics and field emission scanning electron microscopy (FESEM) to examine the changes in architecture accompanying the gradual transition of the inactive to the hyperactive melanotrope cells. The proteomic analysis showed differential expression of neuroendocrine secretory proteins, endoplasmic reticulum (ER)-resident chaperones, and housekeeping and metabolic proteins. The FESEM study revealed changes in the ultrastructure of the ER and Golgi and the number of secretory granules. We conclude that activation of neuroendocrine cells tunes their molecular machineries and organelles to become professional secretors.