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| 2. |
- Haitina, Tatjana, et al.
(författare)
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Functional characterization of two melanocortin (MC) receptors in lamprey showing orthology to the MC1 and MC4 receptor subtypes
- 2007
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 7, s. 101-
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Tidskriftsartikel (refereegranskat)abstract
- Background The melanocortin (MC) receptors have a key role in regulating body weight and pigmentation. They belong to the rhodopsin family of G protein-coupled receptors (GPCRs). The purpose of this study was to identify ancestral MC receptors in agnathan, river lamprey. Results We report cloning of two MC receptors from river lamprey. The lamprey receptors, designated MCa and MCb, showed orthology to the MC1 and MC4 receptor subtypes, respectively. The molecular clock analysis suggested that lamprey MC receptor genes were not duplicated recently and diverged from each other more than 400 MYR ago. Expression and pharmacological characterization showed that the lamprey MCa receptor was able to bind and be activated by both lamprey and human MSH peptides. The lamprey MCa receptor had relatively high affinity for ACTH derived peptides similarly to the fish MC receptors. We found that both of the lamprey MC receptors were expressed in skin, while the MCb receptor was also found in liver, heart and skeletal muscle. Conclusion This study shows presence of MC receptors in agnathans indicating early signs of specific functions of melanocortin receptor subtypes.
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| 3. |
- Haitina, Tatjana, et al.
(författare)
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High diversity in functional properties of melanocortin 1 receptor (MC1R) in divergent primate species is more strongly associated with phylogeny than coat color
- 2007
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 24:9, s. 2001-2008
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Tidskriftsartikel (refereegranskat)abstract
- We have characterized the biochemical function of the melanocortin1 receptor (MC1R), a critical regulator of melanin synthesis,from 9 phylogenetically diverse primate species with varyingcoat colors. There is substantial diversity in melanocyte-stimulatinghormone (MSH) binding affinity and basal levels of activityin the cloned MC1Rs. MSH binding was lost independently in lemurand New World monkey lineages, whereas high basal levels ofMC1R activity occur in lemurs and some New World monkeys andOld World monkeys. Highest levels of basal activity were foundin the MC1R of ruffed lemurs, which have the E94K mutation thatleads to constitutive activation in other species. In 3 species(2 lemurs and the howler monkey), we report the novel findingthat binding and inhibition of MC1R by agouti signaling protein(ASIP) can occur when MSH binding has been lost, thus enablingcontinuing regulation of the melanin type via ASIP expression.Together, these findings can explain the previous paradox ofa predominantly pheomelanic coat in the red ruffed lemur (Vareciarubra). The presence of a functional, MSH-responsive MC1R inorangutan demonstrates that the mechanism of red hair generationin this ape is different from the prevalent mechanism in Europeanhuman populations. Overall, we have found unexpected diversityin MC1R function among primates and show that the evolutionof the regulatory control of MC1R activity occurs by independentvariation of 3 distinct mechanisms: basal MC1R activity, MSHbinding and activation, and ASIP binding and inhibition. Thisdiversity of function is broadly associated with primate phylogenyand does not have a simple relation to coat color phenotypewithin primate clades.
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| 4. |
- Klovins, Janis, et al.
(författare)
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Cloning of two melanocortin (MC) receptors in spiny dogfish : MC3 receptor in cartilaginous fish shows high affinity to ACTH-derived peptides while it has lower preference to gamma-MSH
- 2004
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:21, s. 4320-4331
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Tidskriftsartikel (refereegranskat)abstract
- We report the cloning and characterization of two melanocortin receptors (MCRs) from the spiny dogfish (Squalus acanthias) (Sac). Phylogenetic analysis shows that these shark receptors are orthologues of the MC3R and MC5R subtypes, sharing 65% and 70% overall amino acid identity with the human counterparts, respectively. The SacMC3R was expressed and pharmacologically characterized in HEK293 cells. The radioligand binding results show that this receptor has high affinity for adrenocorticotropic hormone (ACTH)-derived peptides while it has comparable affinity for alpha- and beta-melanocyte stimulating hormone (MSH), and slightly lower affinity for gamma-MSH when compared with the human orthologue. ACTH(1-24) has high potency in a second-messenger cAMP assay while alpha- and gamma-MSH had slightly lower potency in cells expressing the SacMC3R. We used receptor-enhanced green fluorescence protein (EGFP) fusion to show the presence of SacMC3R in plasma membrane of Chinese hamster ovary and HEK293 cells but the SacMC5R was retained in intracellular compartments of these cells hindering pharmacological characterization. The anatomical distribution of the receptors were determined using reverse transcription PCR. The results showed that the SacMC3R is expressed in the hypothalamus, brain stem and telencephalon, optic tectum and olfactory bulbs, but not in the cerebellum of the spiny dogfish while the SacMC5R was found only in the same central regions. This report describes the first molecular characterization of a MC3R in fish. The study indicates that many of the important elements of the MC system existed before radiation of gnathostomes, early in vertebrate evolution, at least 450 million years ago.
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| 5. |
- Ling, Maria K, et al.
(författare)
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The melanocortin receptor subtypes in chicken have high preference to ACTH-derived peptides
- 2004
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Ingår i: British Journal of Pharmacology. - : Wiley. - 0007-1188 .- 1476-5381. ; 143:5, s. 626-637
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Tidskriftsartikel (refereegranskat)abstract
- 1 Melanocortin (MC) receptors are widely distributed throughout the body of chicken, like in mammals, and participate in a wide range of physiological functions. 2 To clarify the pharmacological impact of ligands acting in the MC system, we expressed the chicken MC1, MC2, MC3, MC4 and MC5 (cMC1-5) receptors in eukaryotic cells and performed comprehensive pharmacological characterization of the potency of endogenous and synthetic melanocortin peptides. 3 Remarkably, the cMC receptors displayed high affinity for ACTH-derived peptides and in general low affinity for alpha-MSH. It is evident that not only the cMC2 receptor but also the other cMC receptors interact with ACTH-derived peptide through an epitope beyond the sequence of alpha-MSH. 4 The synthetic ligand MTII was found to be a potent agonist whereas HS024 was a potent antagonist at the cMC4 receptor, indicating that these ligands are suitable for physiological studies in chicken. 5 We also show the presence of prohormone convertase 1 (PC1) and PC2 genes in chicken, and that these peptides are coexpressed with proopiomelanocortin (POMC) in various tissues.
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| 6. |
- Ringholm, Aneta I., 1971-
(författare)
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Cloning, Expression, Pharmacological Characterization and Anatomical Distribution of Melanocortin Receptors in an Evolutionary Perspective
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The melanocortin (MC) receptors are G-protein coupled receptors thatparticipate in several important physiological functions such as the regulation of the energy balance. This thesis focuses on the evolutionary aspect of the MC receptors and their pharmacology.One MC4 receptor and two MC5 receptor subtypes were found in a teleost fish, zebrafish. This indicates that the MC receptor subtypes arose very early in vertebrate evolution. Important pharmacological and functional properties, as well as gene structure and syntenic relationships have been highly conserved over a period of more than 400 million years implying that these receptors participate in vital physiological functions. Moreover, we found a MC4 receptor from a shark, spiny dogfish that represents the most distant MC receptor gene cloned to date. We also characterized the pharmacology of a MC4 receptor in goldfish. The conserved central expression pattern and physiological role in regulation of food intake of the MC4 receptor suggests that neuronal pathways of the melanocortin system may be important for regulation of energy homeostasis in most vertebrates. We determined the chromosomal position of the chicken MC receptors genes and found conserved synteny of the MC2, MC5, and MC4 receptor genes. These results suggest that there exist a clustering of these genes that is ancient. Analysis of conserved synteny with mammalian genomes and paralogon segments prompted us to predict an ancestral gene organization that may explain how this family has been formed through both local duplication and tetraploidization processes.There are several common point mutations in the human MC1 receptor that are over represented in North European red-heads, and in individuals with pale skin. We pharmacologically characterised four naturally occurring human MC1 receptor variants providing molecular explanation to the respective phenotype.The MC receptor subtypes have highly diverse physiological functions despite having relative high similarities in their primary structure. Our studies on the structural and functional properties of the MC receptor subtypes have provided insight into the molecular mechanism of how the specification of these receptors may have occurred.
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| 7. |
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| 8. |
- Ringholm, Aneta, et al.
(författare)
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Pharmacological characterization of loss of function mutations of the human melanocortin 1 receptor that are associated with red hair
- 2004
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Ingår i: Journal of Investigative Dermatology. - 0022-202X .- 1523-1747. ; 123:5, s. 917-923
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Tidskriftsartikel (refereegranskat)abstract
- Variation in skin color is the major host risk factor for melanoma and other forms of skin cancer. Individuals with red hair show an increased ratio of phaeomelanin to eumelanin in both hair and skin. This ratio is regulated by the melanocortin (MC) 1 receptor. There are several common point mutations in the human MC1 receptor that are overrepresented in North European red-heads, and in individuals with pale skin. In order to determine the functional significance of these mutations, we expressed the Asp84Glu, Val92Met, Arg163Gln, and Asp294His variants of the human MC1 receptors in eukaryotic cells and determined their ability to bind alpha-melanocyte stimulating hormone (MSH) peptides and increase intracellular cAMP. The mutants Asp84Glu and Asp294His showed a much lower response to alpha-MSH in cAMP and a slightly impaired ability to bind alpha-MSH, and the Val92Met mutant bound alpha-MSH with 100-fold lower affinity as compared with the wild-type. The Arg163Gln variant, widely found in some Asian populations, reached normal level of cAMP response but had just slightly lower potency for alpha-MSH in binding and second messenger studies. The results provide important pharmacological characterization of common MC1 receptor variants in various world populations.
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| 9. |
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| 10. |
- Schiöth, Helgi B, et al.
(författare)
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Evolutionary conservation of the structural, pharmacological, and genomic characteristics of the melanocortin receptor subtypes
- 2005
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 26:10, s. 1886-1900
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Tidskriftsartikel (refereegranskat)abstract
- We have cloned melanocortin receptors (MCRs) from several species of fish. The MC4R and MC5R subtypes arose early in vertebrate evolution and their primary structure is remarkably conserved. Expression and pharmacological characterization of the MCRs in fish has revealed that they bind and respond to melanocortin peptides with high potency. Detailed characterization of the binding properties of the different subtypes suggests that MCRs in early vertebrates had preference for adrenocorticotropic hormone (ACTH) peptides, while the high sensitivity for the shorter proopiomelanocortin (POMC) products, such as the α-, β-, and γ-melanocyte-stimulating hormone (MSH), has appeared later, perhaps as the MCR subtypes gained more specialized functions. The MCR repertoire shows in general high similarities in their primary structures, while they are however not similar in terms of functional roles. The MCRs serve therefore as an interesting model family to understand the molecular mechanisms of how functions of the genes can diverge during evolution. In this review, we provide an overview of our recent studies on the cloning, expression, pharmacology, 3D modeling, and genomic studies of the MCRs in non-mammalian species.
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