POMC and Human Pigmentation

Proopiomelanocortin or POMC and the neuropeptides derived from it, participate in several cardinal processes that control the central nervous system and peripheral tissues. Although, POMC regulates melanocortin or MC receptors in their local activation process, its role in extracellular proteolytic processing has been largely ignored. Several research scientists have been investigating important mechanisms that have significance in controlling the bio-availability of adrenocorticotropin and hormones that stimulate cutaneous melanocyte. This has been done in the context of peptidases like neprilysin – or neutral endopeptidase or NEP, and the ACE or angiotensin – converting enzyme (König et al, 2006, Pp. 751 - 761).

The skin constitutes a source, as well as a target organ for the actions of neuropeptides derived from proopiomelanocortin or POMC. These peptides are ACTH, α-melanocyte stimulating hormone or α-MCH, and β-endorphin. The levels of POMC genes and corticotropin releasing hormone peptides or CRH peptides are not constant in the skin. Their levels vary due to  several factors, like the physiological changes relating to hair cycles, which are at their zenith during the anagen phase; physiological changes resulting from exposure to ultraviolet radiation; cytokine releases; and the incidence of cutaneous pathology (Slominski et al, 2000, Pp. 979 -1020 ).

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The pro-inflammatory interleukin-1 is a major cytokine that increases the cutaneous levels of POMC mRNA and peptides, and MSH receptors. The CRH or POMC systems undergo a stimulation of expression of all their components, on being exposed to ultraviolet radiation. In addition, the corresponding receptors, also undergo a stimulation of expression (Slominski et al, 2000, Pp. 979 -1020 ).

The cutaneous POMC gene’s molecular characterisation reveals mRNA forms that resemble those to be found in the pituitary, whose expression is conjoined with that of the shorter variants. The cutaneous expression of receptors, in respect of POMC peptides is functional in ...

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