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15 results on '"Ringholm, Aneta"'

9. Functional characterization of two melanocortin (MC) receptors in lamprey showing orthology to the MC1 and MC4 receptor subtypes

Author

Kawauchi Hiroshi, Enberg Johan, Ringholm Aneta, Löwgren Maja, Takahashi Akiyoshi, Klovins Janis, Haitina Tatjana, Larson Earl T, Fredriksson Robert, and Schiöth Helgi B

Subjects
Evolution, QH359-425
Abstract

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.

Published
2007
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10. Cloning, Expression, Pharmacological Characterization and Anatomical Distribution of Melanocortin Receptors in an Evolutionary Perspective

Author

Ringholm, Aneta I.

Subjects
Pharmacology, spiny dogfish, chicken, Farmakologi, Pharmacology and Toxicology, zebrafish, Farmakologi och toxikologi, polymorphism, GPCR, evolution, genome duplication, tetraploidization, pigmentation, melanocortin, MSH
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.

Published
2004

15. 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.

Author

Klovins J, Haitina T, Ringholm A, Löwgren M, Fridmanis D, Slaidina M, Stier S, and Schiöth HB

Subjects
Amino Acid Sequence, Animals, Bacteriophages, Blotting, Southern, CHO Cells, Cell Line, Cloning, Molecular, Cricetinae, Cyclic AMP metabolism, Dogfish, Dose-Response Relationship, Drug, Escherichia coli metabolism, Gene Library, Green Fluorescent Proteins metabolism, Humans, Introns, Kinetics, Melanocyte-Stimulating Hormones chemistry, Molecular Sequence Data, Peptides chemistry, Phylogeny, Polymerase Chain Reaction, Radioligand Assay, Reverse Transcriptase Polymerase Chain Reaction, Sequence Analysis, DNA, Sequence Homology, Amino Acid, Tissue Distribution, Adrenocorticotropic Hormone chemistry, Receptor, Melanocortin, Type 3 genetics, Receptor, Melanocortin, Type 4 genetics, gamma-MSH chemistry
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.

Published
2004
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