Melanocortin receptor
Encyclopedia
Melanocortin receptors are members of the rhodopsin
Rhodopsin
Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...

 family of 7-transmembrane, G protein-coupled receptors.

There are five known members of the melanocortin receptor system each with differing specificities for melanocortin
Melanocortin
The melanocortins are a group of peptide hormones which include adrenocorticotropic hormone and the different forms of melanocyte-stimulating hormone . They can be synthetic . In humans they can be endogenously produced from proopiomelanocortin in the pituitary gland...

s:
. MC1R is associated with pigmentation genetics.. MC2R is also known as the ACTH receptor
ACTH receptor
The ACTH receptor is a type of melanocortin receptor , properly known as MC2, which is specific for ACTH.It is found in the zona fasciculata of the human adrenal cortex. Binding of the receptor by ACTH stimulates the production of cortisol...

 or corticotropin receptor because it is specific for ACTH alone.. MC3R. Defects in MC4R are a cause of autosomal dominant obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

, accounting for 6% of all cases of early-onset obesity.. MC5R
These receptors are inhibited
Receptor antagonist
A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses...

 by endogenous
Endogenous
Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...

 inverse agonist
Inverse agonist
In the field of pharmacology, an inverse agonist is an agent that binds to the same receptor as an agonist but induces a pharmacological response opposite to that agonist....

s agouti signalling peptide
Agouti signalling peptide
Agouti signalling peptide, a product of the Agouti gene, is a peptide consisting of 131 amino acids. Its discovery was published in 1994 in the scientific journal Nature where its functional properties were described...

 and agouti-related peptide
Agouti-related peptide
Agouti-related protein also called Agouti-related peptide is a neuropeptide produced in the brain by the AgRP/NPY neuron. It is only synthesised in NPY containing cell bodies located in the ventromedial part of the arcuate nucleus in the hypothalamus...

, and activated by synthetic
Peptide synthesis
In organic chemistry, peptide synthesis is the production of peptides, which are organic compounds in which multiple amino acids are linked via amide bonds which are also known as peptide bonds...

 (i.e.: afamelanotide
Afamelanotide
Afamelanotide developed at the University of Arizona is a synthetic analog of the naturally-occurring melanocortin peptide hormone alpha-melanocyte stimulating hormone that has been shown to induce skin pigmentation through melanogenesis and thereby subsequently reduce sun damage to UV exposed...

) and endogenous agonist
Agonist
An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

 melanocyte-stimulating hormone
Melanocyte-stimulating hormone
The melanocyte-stimulating hormones are a class of peptide hormones that are produced by cells in the intermediate lobe of the pituitary gland...

s.

Selective Ligands

Several selective ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

s 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
    Afamelanotide
    Afamelanotide developed at the University of Arizona is a synthetic analog of the naturally-occurring melanocortin peptide hormone alpha-melanocyte stimulating hormone that has been shown to induce skin pigmentation through melanogenesis and thereby subsequently reduce sun damage to UV exposed...

  • alpha-MSH
  • Bremelanotide
    Bremelanotide
    Bremelanotide is a compound under drug development by Palatin Technologies as a treatment for hemorrhagic shock and reperfusion injury...

  • Melanotan II
    Melanotan II
    Melanotan II developed at the University of Arizona is a synthetic analog of the naturally occurring melanocortin peptide hormone alpha-melanocyte stimulating hormone that in usage has been shown to have melanogenesis and aphrodisiac effects in preliminary studies and clinical trials...



MC2 selective
  • ACTH
    Adrenocorticotropic hormone
    Adrenocorticotropic hormone , also known as 'corticotropin', 'Adrenocorticotrophic hormone', is a polypeptide tropic hormone produced and secreted by the anterior pituitary gland. It is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological...

  • Cosyntropin
    Cosyntropin
    Cosyntropin is a synthetic derivative of adrenocorticotropic hormone that is used in the ACTH stimulation test to evaluate and diagnose cortisol disorders...

  • Tetracosactide
    Tetracosactide
    Tetracosactide is a synthetic analogue of the naturally occurring adrenocorticotrophic hormone .-Pharmacology:...



MC3 selective
  • gamma-MSH


MC4 selective
  • beta-MSH
  • THIQ
    THIQ
    THIQ is a drug used in scientific research, which is the first non-peptide agonist developed that is selective for the melanocortin receptor subtype MC4. In animal studies, THIQ stimulated sexual activity in rats, but with little effect on appetite or inflammation...


Antagonists and inverse agonists

MC1 selective
  • Agouti signalling peptide
    Agouti signalling peptide
    Agouti signalling peptide, a product of the Agouti gene, is a peptide consisting of 131 amino acids. Its discovery was published in 1994 in the scientific journal Nature where its functional properties were described...



MC4 selective
  • Agouti-related peptide
    Agouti-related peptide
    Agouti-related protein also called Agouti-related peptide is a neuropeptide produced in the brain by the AgRP/NPY neuron. It is only synthesised in NPY containing cell bodies located in the ventromedial part of the arcuate nucleus in the hypothalamus...

    (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)

External links

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