Figure 1.

Regulation of POMC processing and secretion. Human POMC is translated as a 267-amino acid protein that, after removal of the signal peptide, undergoes successive rounds of cleavage and trimming at dibasic residues (blue) in a tissue-specific manner; the hypothalamic pattern is illustrated. Additional levels of post-translational modification include C-terminal amidation (orange) and N-terminal acetylation (magenta). The most extensively characterised POMC-derived peptides that regulate food intake (green) include d-α-MSH(1-13), α-MSH(1-13), β-MSH(1-18), β-EP (1-31) and β-EP (1-27). Illustrated mutations in β-MSH have been associated with obesity, suggesting a role for this peptide in human body weight regulation. The concentrations of secreted POMC-derived peptides may be regulated at the levels of transcription, translation, processing, and secretion. ACTH, adrenocorticotropic hormone; CLIP, corticotropin-like intermediary peptide; EP, endorphin; LPH, lipotropin; MSH, melanocyte stimulating hormone; NPP, POMC N-terminal region; POMC, pro-opiomelanocortin.