Neuroendocrine secretory granules. Highly expressed in adrenal medulla and anterior and posterior pituitary. In the brain, detected in hypothalamus, hippocampus, caudate nucleus, thalamus and, in significantly lower amounts, in the cerebellum. Binds keratan sulfate chains. May be proteolytically processed to give rise to a number of active peptides. This protein is produced by a bicistronic gene which also produces the ALEX protein from an overlapping reading frame. The GNAS locus is imprinted in a complex manner, giving rise to distinct paternally, maternally and biallelically expressed proteins. Shares no sequence similarity with other isoforms due to a novel first exon containing the entire reading frame spliced to shared exon 2 so that exons 2-13 make up the 3'-UTR. Belongs to the NESP55 family.