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Melanocortin 1 receptor genotype: an important determinant of the damage response of melanocytes to ultraviolet radiation.

ABSTRACT: The melanocortin 1 receptor gene is a main determinant of human pigmentation, and a melanoma susceptibility gene, because its variants that are strongly associated with red hair color increase melanoma risk. To test experimentally the association between melanocortin 1 receptor genotype and melanoma susceptibility, we compared the responses of primary human melanocyte cultures naturally expressing different melanocortin 1 receptor variants to ?-melanocortin and ultraviolet radiation. We found that expression of 2 red hair variants abolished the response to ?-melanocortin and its photoprotective effects, evidenced by lack of functional coupling of the receptor, and absence of reduction in ultraviolet radiation-induced hydrogen peroxide generation or enhancement of repair of DNA photoproducts, respectively. These variants had different heterozygous effects on receptor function. Microarray data confirmed the observed differences in responses of melanocytes with functional vs. nonfunctional receptor to ?-melanocortin and ultraviolet radiation, and identified DNA repair and antioxidant genes that are modulated by ?-melanocortin. Our findings highlight the molecular mechanisms by which the melanocortin 1 receptor genotype controls genomic stability of and the mutagenic effect of ultraviolet radiation on human melanocytes.

SUBMITTER: Kadekaro AL

PROVIDER: S-EPMC3229421 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Melanocortin 1 receptor genotype: an important determinant of the damage response of melanocytes to ultraviolet radiation.

Kadekaro Ana Luisa AL Leachman Sancy S Kavanagh Renny J RJ Swope Viki V Cassidy Pamela P Supp Dorothy D Sartor Maureen M Schwemberger Sandy S Babcock George G Wakamatsu Kazumasa K Ito Shosuke S Koshoffer Amy A Boissy Raymond E RE Manga Prashiela P Sturm Richard A RA Abdel-Malek Zalfa A ZA

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20100602 10

The melanocortin 1 receptor gene is a main determinant of human pigmentation, and a melanoma susceptibility gene, because its variants that are strongly associated with red hair color increase melanoma risk. To test experimentally the association between melanocortin 1 receptor genotype and melanoma susceptibility, we compared the responses of primary human melanocyte cultures naturally expressing different melanocortin 1 receptor variants to α-melanocortin and ultraviolet radiation. We found th ...[more]

PMID: 20519635

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Project description:Genetic variation at the melanocortin 1 receptor (MC1R) is an important risk factor for developing ultraviolet (UV) radiation-induced skin cancer, the most common form of cancer in humans. The underlying mechanisms by which the MC1R defends against UV-induced skin cancer are not known. We used neonatal mouse skin (which, like human skin, contains a mixture of melanocytes and keratinocytes) to study how pigment cells and Mc1r genotype affect the genome-level response to UV radiation. Animals without viable melanocytes (Kit(W-v)/Kit(W-v)) or animals lacking a functional Mc1r (Mc1r(e)/Mc1r(e)) were exposed to sunburn-level doses of UVB radiation, and the patterns of large-scale gene expression in the basal epidermis were compared to each other and to nonmutant animals. Our analysis revealed discrete Kit- and Mc1r-dependent UVB transcriptional responses in the basal epidermis. The Kit-dependent UVB response was characterized largely by an enrichment of oxidative and endoplasmic reticulum stress genes, highlighting a distinctive role for pigmented melanocytes in mediating antioxidant defenses against genotoxic stresses within the basal epidermal environment. By contrast, the Mc1r-dependent UVB response contained an abundance of genes associated with regulating the cell cycle and oncogenesis. To test the clinical relevance of these observations, we analyzed publicly available data sets for primary melanoma and melanoma metastases and found that the set of genes specific for the Mc1r-dependent UVB response was able to differentiate between different clinical subtypes. Our analysis also revealed that the classes of genes induced by UVB differ from those repressed by UVB with regard to their biological functions, their overall number, and their size. The findings described here offer new insights into the transcriptional nature of the UV response in the skin and provide a molecular framework for the underlying mechanisms by which melanocytes and the Mc1r independently mediate and afford protection against UV radiation.

Project description:BackgroundHuman skin, which is constantly exposed to solar ultraviolet radiation (UVR), has a unique ability to respond by increasing its pigmentation in a protective process driven by melanogenesis in human epidermal melanocytes (HEMs). However, the molecular mechanisms used by HEMs to detect and respond to UVR remain unclear.ObjectivesTo investigate the function and potential mechanism of opsin 5 (OPN5), a photoreceptor responsive to UVR wavelengths, in melanogenesis in HEMs.MethodsMelanin content in HEMs was determined using the NaOH method, and activity of tyrosinase (TYR) (a key enzyme in melanin synthesis) was determined by the l-DOPA method. OPN5 expression in UVR-treated vs. untreated HEMs and explant tissues was detected by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), Western blotting and immunofluorescence. Short interfering RNA-mediated OPN5 knockdown and a lentivirus OPN5 overexpression model were used to examine their respective effects on TYR, tyrosinase-related protein 1 (TRP1), TRP2 and microphthalmia-associated transcription factor (MITF) expression, under UVR. Changes in expression of TYR, TRP1 and TRP2 caused by changes in OPN5 expression level were detected by RT-qPCR and Western blot. Furthermore, changes in signalling pathway proteins were assayed.ResultsWe found that OPN5 is the key sensor in HEMs responsible for UVR-induced melanogenesis. OPN5-induced melanogenesis required Ca2+ -dependent G protein-coupled receptor- and protein kinase C signal transduction, thus contributing to the UVR-induced MITF response to mediate downstream cellular effects, and providing evidence of OPN5 function in mammalian phototransduction. Remarkably, OPN5 activation was necessary for UVR-induced increase in cellular melanin and has an inherent function in melanocyte melanogenesis.ConclusionsOur results provide insight into the molecular mechanisms of UVR sensing and phototransduction in melanocytes, and may reveal molecular targets for preventing pigmentation or pigment diseases.

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Melanocortin 1 receptor genotype: an important determinant of the damage response of melanocytes to ultraviolet radiation.

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Melanocortin 1 receptor genotype: an important determinant of the damage response of melanocytes to ultraviolet radiation.

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