Melanocortin receptor

Melanocortin receptors are members of the rhodopsin family of 7-transmembrane, G protein-coupled receptors.

There are five known members of the melanocortin receptor system each with differing specificities for melanocortins:

These receptors are inhibited by endogenous inverse agonists agouti signalling peptide and agouti-related peptide, and activated by synthetic (i.e.: afamelanotide) and endogenous agonist melanocyte-stimulating hormones.
 * . MC1R is associated with pigmentation genetics.
 * . MC2R is also known as the ACTH receptor or corticotropin receptor because it is specific for ACTH alone.
 * . MC3R
 * . Defects in MC4R are a cause of autosomal dominant obesity, accounting for 6% of all cases of early-onset obesity.
 * . MC5R

Selective Ligands
Several selective ligands for the melanocortin receptors are known,   and some synthetic compounds have been investigated as potential tanning, anti-obesity and aphrodisiac drugs, with tanning effects mainly from stimulation of MC1, while anorectic and aphrodisiac effects appear to involve both MC3 and MC4. MC1, MC3 and MC4 are widely expressed in the brain, and are also thought to be responsible for effects on mood and cognition.

Agonists

 * Non-selective
 * Afamelanotide
 * alpha-MSH
 * Bremelanotide
 * Melanotan II


 * MC2 selective
 * ACTH
 * Cosyntropin
 * Tetracosactide


 * MC3 selective
 * gamma-MSH


 * MC4 selective
 * beta-MSH
 * THIQ

Antagonists and inverse agonists

 * MC1 selective
 * Agouti signalling peptide


 * MC4 selective
 * Agouti-related peptide (inverse agonist at both MC3 and MC4)
 * HS-014
 * HS-024
 * MCL-0042
 * MCL-0129
 * MPB-10
 * SHU-9119 (agonist at MC1 and MC5, antagonist at MC3 and MC4)