title: Further evidence on acetylation-induced inhibition of the pigment-dispersing activity of α-melanocyte-stimulating hormone.
abstract: Our previous studies showed that in barfin flounder, α-melanocyte-stimulating hormone (α-MSH) stimulates pigment dispersion in xanthophores, while it shows negligible effects in melanophores. The present study was undertaken to evaluate whether these results are limited to barfin flounder by using Japanese flounder. Three subtypes of proopiomelanocortin gene encoding melanocortins (MCs) were expressed in the Japanese flounder pituitary, one of which was also expressed in the skin. Expression of melanocortin 5 receptor gene (Mc5r) was observed in isolated xanthophores, while that of Mc1r and Mc5r was found in melanophores. In the xanthophores of Japanese flounder skin, α-MSH as well as desacetyl (Des-Ac)-α-MSH and diacetyl (Di-Ac)-α-MSH exhibited dose-dependent pigment-dispersing activities, indicating that the signals of α-MSH-related peptides were mediated by MC5R. On the other hand, α-MSH did not stimulate pigment dispersion in melanophores, while Des-Ac-α-MSH and Di-Ac-α-MSH did, thus indicating that the expression of two different types of Mcr is related to the decrease in α-MSH activity. Thus, the molecular repertoire in MC system observed in Japanese flounder is similar to that in barfin flounder. Moreover, the relationship between the pigment-dispersing activities of α-MSH-related peptides and the expression of Mcr subtypes in xanthophores and melanophores were also similar between Japanese flounder and barfin flounder. Consequently, we hypothesize that inhibition of α-MSH activity could be due to the formation of heterodimers comprising MC1R and MC5R, often observed in G-protein-coupled receptors.
authors.affiliation: School of Marine Biosciences, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Kanta
authors.initials: K
authors.lastname: Mizusawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Chiba
authors.forename: Masatomo
authors.initials: M
authors.lastname: Tagawa
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Takahashi
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000818:Animals; D019281:Dimerization; D005432:Flounder / Q000502:physiology*; D008547:Melanophores / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010860:Pigments, Biological / Q000502:physiology*; D011333:Pro-Opiomelanocortin / Q000235:genetics; D044102:Receptor, Melanocortin, Type 1 / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D044103:Receptor, Melanocortin, Type 2 / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D044105:Receptor, Melanocortin, Type 4 / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D044101:Receptors, Melanocortin / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D012879:Skin Physiological Phenomena; D013045:Species Specificity; D000521:alpha-MSH / Q000502:physiology*
chemical_list: D010860:Pigments, Biological; D044102:Receptor, Melanocortin, Type 1; D044103:Receptor, Melanocortin, Type 2; D044105:Receptor, Melanocortin, Type 4; D044101:Receptors, Melanocortin; C086971:melanocortin 5 receptor; D000521:alpha-MSH; D011333:Pro-Opiomelanocortin