Differential expressions of melanocortin receptor subtypes in melanophores and xanthophores of barfin flounder

• Published in: General and comparative endocrinology 2010-08, Vol.168 (1), p.133-142
• Main Authors: Kobayashi, Yuki, Tsuchiya, Keisuke, Yamanome, Takeshi, Schiöth, Helgi B, Takahashi, Akiyoshi
• Format: Article
• Language: English
• Subjects: alpha-MSH - metabolism; Amino Acid Sequence; Animals; Base Sequence; Biologi; Biology; Chromatophores - metabolism; Desacetyl-α-MSH; Endocrinology & Metabolism; FARMACI; Fish Proteins - chemistry; Fish Proteins - classification; Fish Proteins - genetics; Fish Proteins - metabolism; Flounder; Flounder - metabolism; Marine; MEDICIN; MEDICINE; Melanocortin receptor; Melanophores; Melanophores - metabolism; Molecular Sequence Data; NATURAL SCIENCES; NATURVETENSKAP; PHARMACY; Phylogeny; Pigment dispersion; Pleuronectiformes; Protein Binding; Receptors, Melanocortin - chemistry; Receptors, Melanocortin - classification; Receptors, Melanocortin - genetics; Receptors, Melanocortin - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Xanthophores; α-Melanocyte-stimulating hormone
• ISSN: 0016-6480; 1095-6840; 1095-6840
• DOI: 10.1016/j.ygcen.2010.04.017

Abstract α-Melanocyte-stimulating hormone (α-MSH) is a member of the melanocortin (MC) family, and the MC receptor (MCR) is a member of the G protein-coupled receptor (GPCR) superfamily. We previously found that in barfin flounder, a flatfish, α-MSH with an acetyl group at the N-terminus stimulated pigment dispersion in xanthophores; however, this effect was not observed in melanophores. Therefore, the present study was undertaken to find which MCR subtypes are expressed in these pigment cells in order to elucidate how acetylation regulates activities of α-MSH-related peptides. Here, we also report the cloning of Mc1r and Mc5r from barfin flounder. Three types of cells—melanophores, xanthophores, and nonchromatophoric dermal cells—were isolated from the skin samples collected from the dorsal fin. These cells were then tested for the expression of Mc1r and Mc5r as well as Mc2r and Mc4r that we had previously cloned. Mc1r and Mc5r transcripts were detected in melanophores, and a sole Mc5r transcript was detected in xanthophores. We had previously found that the efficiency of α-MSH was higher than that of desacetyl-α-MSH for pigment dispersion in xanthophores. Acetylated MSH peptide may have increased binding affinity to MC5R, whereas α-MSH lacks melanin-dispersing activity. Increasing evidences indicate that many GPCRs form heterodimers, and this may affect the affinity of the ligand for the corresponding GPCR. Taken together, the expression of two different Mcr subtypes in melanophores may suggest that a heterodimer consisting of MC1R and MC5R may have a low binding affinity toward α-MSH. The present results clarify the types of MCRs that are expressed in melanophores and xanthophores of barfin flounder; furthermore, the results provide important clues about the functional regulation of α-MSH-related peptides.