FIGURE 6.

Regulatory processes for secretion of pro-opiomelanocortin (POMC) and its peptides. A: POMC moves from the trans-Golgi network (TGN) to immature secretory granules (ISG) and is secreted from cells by constitutive secretion. Pro-hormone convertase (PC) 1 cleaves POMC to produce adrenocorticotropic hormone (ACTH) which is stored in dense-core secretory granules (DCSGs) before secretion is stimulated. B: on stimulation, α-melanocyte stimulating hormone (MSH) and possibly ACTH is released from the cells in the hypothalamus/skin/pars intermedia of the anterior lobe of the pituitary. C: acute corticotropin releasing hormone (CRH) stimulation in the anterior pituitary causes the release of ACTH. POMC is also released but not subject to stimulation. D: long-term CRH stimulation upregulates the POMC gene and release of ACTH. E: glucocorticoids (Gcs) can inhibit ACTH secretion in an acute, nongenomic manner in the anterior pituitary. F: chronic exposure to glucocorticoids inhibits POMC transcription and ACTH release. [Adapted from Stevens and White (384), with permission from Springer Nature.]