The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones known as the melanocortins, which include adrenocorticotropic hormone (ACTH) and the different forms of melanocyte-stimulating hormone (MSH). It is coupled to Gαs and upregulates levels of cAMP by activating adenylyl cyclase in cells expressing this receptor. It is normally expressed in skin and melanocytes, and to a lesser degree in periaqueductal gray matter, astrocytes and leukocytes. In skin cancer, MC1R is highly expressed in melanomas but not carcinomas.
Model of melanocortin receptors and erythropoiesis
MC1R deficiency and osteoarthritis
Zebrafish MC1R mediates the response of fish chromatophores on exposure to dark (top), in comparison to light (bottom), environments.
Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics, exposure to the sun, disorders, or some combination thereof. Differences across populations evolved through natural selection or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin.
Extended Coloured (Afrikaans: Kleurlinge or Bruinmense) family from South Africa showing some spectrum of human skin coloration
Former Chief Justice of India, P. Sathasivam, has vitiligo
A suntanned arm showing darker skin where it has been exposed. This pattern of tanning is often called a farmer's tan.