Defining the Contribution of MC1R Physiological Ligands to ATR Phosphorylation at Ser435, a Predictor of DNA Repair in Melanocytes.

Abstract

The melanocortin 1 receptor (MC1R), a GS-coupled receptor that signals through cAMP and protein kinase A (PKA), regulates pigmentation, adaptive tanning, and melanoma resistance. MC1R-cAMP signaling promotes PKA-mediated phosphorylation of ataxia telangiectasia and rad3-related (ATR) at Ser435 (ATR-pS435), a modification that enhances nucleotide excision repair (NER) by facilitating recruitment of the XPA protein to sites of UV-induced DNA damage. High-throughput methods were developed to quantify ATR-pS435, measure XPA-photodamage interactions, and assess NER function. We report that melanocyte-stimulating hormone (α-MSH) or ACTH induce ATR-pS435, enhance XPA's association with UV-damaged DNA and optimize melanocytic NER. In contrast, MC1R antagonists agouti signaling protein (ASIP) or human β-defensin 3 (HBD3) interfere with ATR-pS435 generation, impair the XPA-DNA interaction, and reduce DNA repair. Although ASIP and HBD3 each blocked α-MSH-mediated induction of the signaling pathway, only ASIP depleted basal ATR-pS435. Our findings confirm that ASIP diminishes agonist-independent MC1R basal signaling whereas HBD3 is a neutral MC1R antagonist that blocks activation by melanocortins. Furthermore, our data suggest that ATR-pS435 may be a useful biomarker for the DNA repair-deficient MC1R phenotype.

• Authors: Stuart G Jarrett, Erin M Wolf Horrell, Mary C Boulanger, John A D'Orazio
• Journal: The Journal of investigative dermatology (J Invest Dermatol) Vol. 135 Issue 12 Pg. 3086-3095 (Dec 2015) ISSN: 1523-1747 [Electronic] United States
• PMID: 26168232 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Agouti Signaling Protein
• Biomarkers
• DEFB103A protein, human
• Receptor, Melanocortin, Type 1
• XPA protein, human
• Xeroderma Pigmentosum Group A Protein
• beta-Defensins
• Serine
• DNA
• ATR protein, human
• Ataxia Telangiectasia Mutated Proteins
• Cyclic AMP-Dependent Protein Kinases

Topics

• Agouti Signaling Protein (pharmacology)
• Ataxia Telangiectasia Mutated Proteins (metabolism)
• Biomarkers
• Cells, Cultured
• Cyclic AMP-Dependent Protein Kinases (physiology)
• DNA (metabolism)
• DNA Repair
• Humans
• Melanocytes (metabolism)
• Phosphorylation
• Receptor, Melanocortin, Type 1 (physiology)
• Serine (metabolism)
• Xeroderma Pigmentosum Group A Protein (metabolism)
• beta-Defensins (pharmacology)