FIGURE 3.

Pro-opiomelanocortin (POMC) processing in neurons. POMC processing begins in the trans-Golgi network (TGN) which is based in the cell body in the arcuate nucleus (ARC). Very little is known about the sites of processing as the peptides move to the neuronal terminals in the paraventricular nucleus (PVN). There is some suggestion that N-acetyltransferase (N-AT) converts des-acetyl α-MSH (des-α-MSH) to α-MSH at the neuronal terminal such that α-MSH is released to activate melanocortin 4 receptor (MC4R) and decrease food intake (258, 312). POMC can also be processed in the nucleus tractus solitarius (NTS), where less is known about the processing of des-acetyl α-MSH and acetylated β-endorphin (β-EP) are the prominent peptides generated.