title: 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.affiliation: Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Jarrett
authors.affiliation: Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA; Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Wolf Horrell
authors.affiliation: Department of Dietetics and Human Nutrition, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Boulanger
authors.affiliation: Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA; Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky, USA; Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, Kentucky, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA; Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA. Electronic address: jdorazio@uky.edu.
authors.forename: John A
authors.initials: JA
authors.lastname: D'Orazio
mesh_terms: D054366:Agouti Signaling Protein / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D015415:Biomarkers; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004247:DNA / Q000378:metabolism; D004260:DNA Repair; D006801:Humans; D008544:Melanocytes / Q000378:metabolism*; D010766:Phosphorylation; D044102:Receptor, Melanocortin, Type 1 / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D051760:Xeroderma Pigmentosum Group A Protein / Q000378:metabolism; D023083:beta-Defensins / Q000494:pharmacology
chemical_list: D054366:Agouti Signaling Protein; D015415:Biomarkers; C422950:DEFB103A protein, human; D044102:Receptor, Melanocortin, Type 1; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; D023083:beta-Defensins; D012694:Serine; D004247:DNA; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017868:Cyclic AMP-Dependent Protein Kinases