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Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
Published on: September 7, 2013
Selected melanocortin 1 receptor single-nucleotide polymorphisms differentially alter multiple signaling pathways.
J R Doyle1, J P Fortin, M Beinborn
1Molecular Pharmacology Research Center, Molecular Cardiology Research Institute, Tufts Medical Center, Boston, Massachusetts, USA.
Investigating melanocortin 1 receptor (MC1R) single-nucleotide polymorphisms (SNPs) reveals altered signaling. Certain MC1R variants, like F196L, show reduced function, but small molecules may restore activity.
Area of Science:
- Pharmacology and Molecular Biology
- G protein-coupled receptor (GPCR) research
- Genetics and cellular signaling
Background:
- The melanocortin 1 receptor (MC1R) is a crucial G protein-coupled receptor involved in pigmentation and inflammation.
- MC1R exhibits significant genetic polymorphism, with single-nucleotide polymorphisms (SNPs) potentially altering its function.
- Understanding the functional impact of MC1R SNPs is vital for comprehending variations in pigmentation and inflammatory responses.
Purpose of the Study:
- To investigate the pharmacological effects of specific MC1R single-nucleotide polymorphisms (SNPs): V60L, R163Q, and F196L.
- To assess how these MC1R variants influence basal and ligand-induced cAMP and mitogen-activated protein kinase (MAPK) signaling.
- To explore the potential of small-molecule agonists to rescue the function of impaired MC1R variants.
Main Methods:
- Transient expression of MC1R variants (V60L, R163Q, F196L) in human embryonic kidney 293 cells.
- Assessment of cAMP signaling using luciferase reporter gene assays.
- Evaluation of MAPK activation via Western blot analysis and phospho-extracellular signal-regulated kinase (pERK) detection.
- In vitro inflammation model using A549 cells to assess inflammatory responses.
Main Results:
- All MC1R variants exhibited reduced basal cAMP activity, with V60L and F196L showing decreased surface expression.
- The F196L variant displayed significantly reduced potency for both the peptide agonist α-melanocyte-stimulating hormone (α-MSH) and the small-molecule agonist BMS-470539.
- F196L showed diminished MAPK activation by both α-MSH and BMS-470539, while R163Q selectively lost α-MSH-induced MAPK activation but retained responsiveness to BMS-470539.
- F196L expression enhanced inflammatory responses in A549 cells, an effect reversed by BMS-470539 treatment.
Conclusions:
- Distinct MC1R SNPs are associated with novel and varied signaling profiles.
- The F196L SNP significantly impairs MC1R signaling and enhances inflammatory responses.
- Small-molecule agonists, such as BMS-470539, hold therapeutic potential for restoring the function of MC1R variants with diminished activity.
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