Search results
Results From The WOW.Com Content Network
The prevalence of red hair in humans varies considerably worldwide. In the United States, about 25% of the human population carries the mutated melanocortin 1 receptor that causes red hair. With one in four people as carriers, the chance of two people having a child with red hair is about 2% (one in 64). [11]
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 [ 1 ] each with differing specificities for melanocortins : [ 2 ] [ 3 ] [ 4 ]
The five melanocortin receptors are seven-transmembrane G-protein coupled receptors with differing ligand affinities, tissue and cell type expression, and downstream functions. [7] MC1R is expressed on melanocytes , macrophages , epithelial cells, endothelial cells, fibroblasts , monocytes and numerous other immune cells, but is also present in ...
Acting through melanocortin 1 receptor, α-MSH stimulates the production and release of melanin (a process referred to as melanogenesis) by melanocytes in skin and hair. [5]: 1210 Acting in the hypothalamus, α-MSH suppresses appetite. [4]: 419 α-MSH secreted in the hypothalamus also contributes to sexual arousal. [6]
Activation of the MC 1 receptor is responsible for its effect on pigmentation, whereas its regulation of appetite, metabolism, and sexual behavior is mediated through both the MC 3 and MC 4 receptors. It is generated as a proteolyic cleavage product from ACTH (1-13), which is in turn a cleavage product of proopiomelanocortin (POMC).
It is a melanocortin receptor agonist and binds predominantly to the MC 1 receptor. Its binding lasts longer than that of α-MSH. This results in part from afamelanotide's resistance to immediate degradation by serum or proteolytic enzymes. It is thought to cause skin darkening by binding to the MC 1 receptor which in turn drives melanogenesis. [3]
Bennu's icy parent body, perhaps about 60 miles (100 km) in diameter, appears to have formed in the outer solar system and was later destroyed, possibly 1-2 billion years ago.
The melanocortin system is a critical regulator of energy balance, in both feeding behaviors and energy expenditure, [1] as well as peripheral tissues such as skin and hair. [2] This system is a principal nexus of body weight regulation through its role in appetite and energy expenditure via leptin , ghrelin and agouti-related protein .