Category: signaling
Melanocortin receptors (MC1-5R) — Gs-coupled GPCRs activated by POMC-derived peptides (α-MSH, β-MSH, γ-MSH, ACTH). MC1R on melanocytes mediates eumelanin synthesis (skin pigmentation); MC2R is the ACTH receptor on adrenal cortex; MC3R + MC4R in hypothalamus regulate appetite + energy balance; MC5R has thermoregulation + exocrine roles. Therapeutic / research peptides: setmelanotide (Imcivree) — MC4R-selective agonist for monogenic obesity (POMC, PCSK1, LEPR deficiency, BBS); pt-141 (bremelanotide) — MC1R/MC3R/MC4R nonselective agonist for hypoactive sexual desire disorder (premenopausal women); melanotan-ii — MC1R-biased nonselective agonist marketed as tanning peptide (unregulated; melanoma risk + nausea + spontaneous erections). α-MSH is the canonical endogenous ligand.