title: Characterization of three corticotropin-releasing factor receptors in catfish: a novel third receptor is predominantly expressed in pituitary and urophysis.
abstract: The present study reports the isolation of three complementary DNA (cDNA) clones encoding distinct subtypes of CRF receptors from the diploid catfish (cf) species, Ameiurus nebulosus. The first clone encodes a 446-amino acid protein (cfCRF-R1) that is highly homologous to mouse (m) CRF-R1 (93% identical). The cfCRF-R1 messenger RNA is highly expressed in the brain, and its distribution pattern correlates well with that of mammalian CRF-R1, except for weak expression in the pituitary. When transiently expressed in COS-7 cells, cfCRF-R1 bound CRF, urotensin I, and sauvagine with similar affinities. The second full-length cDNA, which was cloned from catfish heart, encodes a 406-amino acid protein that showed homology to murine CRF-R2 (88%) and when expressed in COS-7 cells preferentially bound sauvagine. The highest level of cfCRF-R2 expression was observed in the heart. The third full-length cDNA clone, which encodes a 428-amino acid protein, is structurally closer to cfCRF-R1 (85%) than to cfCRF-R2 (80%). This novel CRF receptor (cfCRF-R3) bound CRF with a 5-fold higher affinity than urotensin I and sauvagine and was expressed in the pituitary gland, urophysis, and brain. The presence of three different CRF receptors, each with distinct tissue distribution and ligand binding properties, suggests a complex CRF/urotensin I system.
authors.affiliation: Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: M
authors.initials: M
authors.lastname: Arai
authors.forename: I Q
authors.initials: IQ
authors.lastname: Assil
authors.forename: A B
authors.initials: AB
authors.lastname: Abou-Samra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000502:physiology*; D019556:COS Cells; D002397:Catfishes; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D017124:Conserved Sequence; D006031:Glycosylation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009490:Neurosecretory Systems / Q000502:physiology*; D009928:Organ Specificity; D010802:Phylogeny; D010902:Pituitary Gland / Q000502:physiology*; D018019:Receptors, Corticotropin-Releasing Hormone / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014981:Xenopus; D000099052:CRF Receptor, Type 1
chemical_list: C101531:CRF receptor type 2; C420457:CRF receptor type 3; D018019:Receptors, Corticotropin-Releasing Hormone; D000099052:CRF Receptor, Type 1