tailieunhanh - Báo cáo khoa học: Characterization and functional expression of cDNAs encoding thyrotropin-releasing hormone receptor from Xenopus laevis Identification of a novel subtype of thyrotropin-releasing hormone receptor

Thyrotropin-releasing hormone receptor (TRHR) has already been cloned in mammals where thyrotropin-releas-inghormone (TRH) isknowntoactasapowerful stimulator of thyroid-stimulating hormone (TSH) secretion. The TRH receptor of amphibians has not yet been characterized, although TRH is specifically important in the adaptation of skin color to environmental changes via the secretion of a-melanocyte-stimulating hormone (a-MSH). | Eur. J. Biochem. 269 4566-4576 2002 FEBS 2002 doi Characterization and functional expression of cDNAs encoding thyrotropin-releasing hormone receptor from Xenopus laevis Identification of a novel subtype of thyrotropin-releasing hormone receptor Isabelle Bidaud1 Philippe Lory2 Pierre Nicolas1 Marc Bulant1 and Ali Ladram1 1 Laboratoire de Bioactivation des Peptides Institut Jacques Monod CNRS-Universite Paris Paris 2Institut de Genetique Humaine CNRS-UPR 1142 Montpellier France Thyrotropin-releasing hormone receptor TRHR has already been cloned in mammals where thyrotropin-releasing hormone TRH is known to act as a powerful stimulator of thyroid-stimulating hormone TSH secretion. The TRH receptor of amphibians has not yet been characterized although TRH is specifically important in the adaptation of skin color to environmental changes via the secretion of a-melanocyte-stimulating hormone a-MSH . Using a degenerate PCR strategy we report on the isolation of three distinct cDNA species encoding TRHR from the brain of Xenopus laevis. We have designated these as xTRHR1 xTRHR2 and xTRHR3. Analysis of the predicted amino acid sequences revealed that the three Xenopus TRHRs are only 54-62 identical and contain all the highly conserved residues constituting the TRH binding pocket. Amino acid sequences and phylogenetic analysis revealed that xTRHR1 is a member of TRHR subfamily 1 and xTRHR2 belongs to subfamily 2 while xTRHR3 is a new TRHR subtype awaiting discovery in other animal species. The three Xeno-pus TRHRs have distinct patterns of expression. xTRHR3 was abundant in the brain and much scarcer in the peripheral tissues whereas xTRHR1 was found mainly in the stomach and xTRHR2 in the heart. The Xenopus TRHR subtype 1 was found specifically in the intestine lung and urinary bladder. These observations suggest that the three xTRHRs each have specific functions that remain to be elucidated. Expression in Xenopus oocytes and HEK-293 cells