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Loss-of-function variants of the human melanocortin-1 receptor gene in melanoma cells define structural determinants of receptor function.
- Source :
-
European journal of biochemistry [Eur J Biochem] 2002 Dec; Vol. 269 (24), pp. 6133-41. - Publication Year :
- 2002
-
Abstract
- The alpha-melanocyte-stimulating hormone (alphaMSH) receptor (MC1R) is a major determinant of mammalian skin and hair pigmentation. Binding of alphaMSH to MC1R in human melanocytes stimulates cell proliferation and synthesis of photoprotective eumelanin pigments. Certain MC1R alleles have been associated with increased risk of melanoma. This can be theoretically considered on two grounds. First, gain-of-function mutations may stimulate proliferation, thus promoting dysplastic lesions. Second, and opposite, loss-of-function mutations may decrease eumelanin contents, and impair protection against the carcinogenic effects of UV light, thus predisposing to skin cancers. To test these possibilities, we sequenced the MC1R gene from seven human melanoma cell (HMC) lines and three giant congenital nevus cell (GCNC) cultures. Four HMC lines and two GCNC cultures contained MC1R allelic variants. These were the known loss-of-function Arg142His and Arg151Cys alleles and a new variant, Leu93Arg. Moreover, impaired response to a superpotent alphaMSH analog was demonstrated for the cell line carrying the Leu93Arg allele and for a HMC line homozygous for wild-type MC1R. Functional analysis in heterologous cells stably or transiently expressing this variant demonstrated that Leu93Arg is a loss-of-function mutation abolishing agonist binding. These results, together with site-directed mutagenesis of the vicinal Glu94, demonstrate that the MC1R second transmembrane fragment is critical for agonist binding and maintenance of a resting conformation, whereas the second intracellular loop is essential for coupling to the cAMP system. Therefore, loss-of-function, but not activating MC1R mutations are common in HMC. Their study provides important clues to understand MC1R structure-function relationships.
- Subjects :
- Alleles
Amino Acid Sequence
Animals
Arginine chemistry
Blotting, Western
CHO Cells
Cell Line
Cell Membrane metabolism
Cells, Cultured
Cloning, Molecular
Cricetinae
Cyclic AMP metabolism
DNA, Complementary metabolism
Dose-Response Relationship, Drug
Heterozygote
Homozygote
Humans
Leucine chemistry
Melanoma metabolism
Mice
Molecular Sequence Data
Mutagenesis, Site-Directed
Protein Conformation
Protein Structure, Tertiary
Receptors, Corticotropin physiology
Receptors, Melanocortin
Sequence Homology, Amino Acid
Structure-Activity Relationship
Tumor Cells, Cultured
Ultraviolet Rays
Melanoma genetics
Mutation
Receptors, Corticotropin genetics
Subjects
Details
- Language :
- English
- ISSN :
- 0014-2956
- Volume :
- 269
- Issue :
- 24
- Database :
- MEDLINE
- Journal :
- European journal of biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 12473109
- Full Text :
- https://doi.org/10.1046/j.1432-1033.2002.03329.x