title: Molecular cloning, molecular evolution and gene expression of cDNAs encoding thyrotropin-releasing hormone receptor subtypes in a teleost, the sockeye salmon (Oncorhynchus nerka).
abstract: Molecular cloning of thyrotropin-releasing hormone receptors (TRHR) was performed in a teleost, the sockeye salmon (Oncorhynchus nerka). Four different TRHR cDNAs were cloned and named TRHR1, TRHR2a, TRHR2b and TRHR3 based on their similarity to known TRHR subtypes in vertebrates. Important residues for TRH binding were conserved in deduced amino acid sequences of the three TRHR subtypes except for the TRHR2b. Seven transmembrane domains were predicted for TRHR1, TRHR2a and TRHR3 proteins but only five for TRHR2b which appears to be truncated. In silico database analysis identified putative TRHR sequences including invertebrate TRHR and reptilian, avian and mammalian TRHR3. Phylogenetic analyses predicted the molecular evolution of TRHR in vertebrates: from the common ancestral TRHR (i.e. invertebrate TRHR), the TRHR2 subtype diverged first and then TRHR1 and TRHR3 diverged. Reverse transcription-polymerase chain reaction analyses revealed TRHR1 transcripts in the brain (hypothalamus), retina, pituitary gland and large intestine; TRHR2a in the brain (telencephalon and hypothalamus); and TRHR3 in the brain (olfactory bulbs) and retina.
authors.affiliation: Department of Biotechnology, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Saito
authors.forename: Miyuki
authors.initials: M
authors.lastname: Mekuchi
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Kimura
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Aoki
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Masuda
authors.forename: Teruo
authors.initials: T
authors.lastname: Azuma
authors.forename: Motohiro
authors.initials: M
authors.lastname: Fukami
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iigo
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yanagisawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000235:genetics; D008969:Molecular Sequence Data; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012474:Salmon / Q000235:genetics*; D020539:Sequence Analysis, Protein
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D018025:Receptors, Thyrotropin-Releasing Hormone