Melanocortin (MC) Receptors

Melanocortin receptors (MCRs) comprise a family of five, class A, G protein-coupled receptors designated MC1R-MC5R with diverse physiological roles. MCRs are found in chordates and are regarded as having evolved from a single ancestral receptor, possibly corresponding most closely to MC4R. Signaling by MCRs has primarily been observed as occurring through the stimulatory α unit Gs which activates adenylyl cyclase to produce cAMP.

The central nervous melanocortin system is involved in energy homeostasis, regulating food intake and energy expenditure. The brain melanocortin system is defined as the primary neurons that express neuropeptide ligands, and secondary neurons expressing the predominant neural melanocortin receptors (MC3R, MC4R). Mutations in the gene encoding melanocortin receptor agonists, or the genes encoding MC3R or MC4R cause obesity. The other members of the melanocortin receptor family are primarily expressed in the periphery, and are involved in regulating pigmentation (MC1R), adrenal gland function (MC2R), immune function (MC1R/MC3R), and sebaceous gland activity (MC5R).