The melanocortin-4 receptor (MC4R) is a member of the superfamily of seven transmembrane G-protein coupled receptors that are involved in multiple signal transduction pathways including the cAMP and MAPK signaling pathways.  It is thought that the melanocortin system modulates energy expenditure and insulin sensitivity; activation of the MC4R results in the inhibition of c-Jun N-terminal kinase (JNK) activity and promotes insulin signaling.  MC4R-null mice display maturity onset obesity characterized by hyperphagia, increased adiposity, hyperinsulinaemia and hyperleptinaemia, suggesting that like other obesity-linked genes such as FTO, PTER, and NPC1, MC4R is a potential candidate target for the treatment of obesity.