Identification of the chicken growth hormone-releasing hormone receptor (GHRH-R) mRNA and gene: regulation of anterior pituitary GHRH-R mRNA levels by homologous and heterologous hormones.
GHRH stimulates GH secretion in chickens as in mammals. However, nothing is known about the chicken GHRH receptor (GHRH-R). Here we report the cDNA sequence of chicken GHRH-R. Comparison of the cDNA sequence with the chicken genome localized the GHRH-R gene to chicken chromosome 2 and indicated that the chicken GHRH-R gene consists of 13 exons. Expression of all exons was confirmed by RT-PCR amplification of pituitary mRNA. The amino acid sequence predicted by the GHRH-R cDNA is homologous to that in other vertebrates and contains seven transmembrane domains and a conserved hormone-binding domain. The predicted size of the GHRH-R protein (48.9 kDa) was confirmed by binding of (125)I-GHRH to chicken pituitary membranes and SDS-PAGE. GHRH-R mRNA was readily detected by RT-PCR in the pituitary but not in the hypothalamus, total brain, lung, adrenal, ovary, or pineal gland. Effects of corticosterone (CORT), GHRH, ghrelin, pituitary adenylate cyclase-activating peptide, somatostatin (SRIF), and TRH on GHRH-R and GH gene expression were determined in cultures of chicken anterior pituitary cells. GHRH-R and GH mRNA levels were determined by quantitative real-time RT-PCR. Whereas all treatments affected levels of GH mRNA, only CORT, GHRH, and SRIF significantly altered GHRH-R mRNA levels. GHRH-R gene expression was modestly increased by GHRH and suppressed by SRIF at 4 h, and CORT dramatically decreased levels of GHRH-R mRNA at 72 h. We conclude that adrenal glucocorticoids may substantially impact pituitary GH responses to GHRH in the chicken through modulation of GHRH-R gene expression.
Porter
Tom E
TE
Department of Animal and Avian Sciences, University of Maryland, College Park, 20742, USA.
Ellestad
Laura E
LE
Fay
Allison
A
Stewart
Joanna L
JL
Bossis
Ioannis
I
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000196:embryology; D002478:Cells, Cultured; D002645:Chickens; D002874:Chromosome Mapping; D019295:Computational Biology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005091:Exons; D005260:Female; D005786:Gene Expression Regulation; D015723:Gene Library; D007031:Hypothalamus / Q000378:metabolism; D007438:Introns; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000235:genetics* / Q000502:physiology*; D018017:Receptors, Pituitary Hormone-Regulating Hormone / Q000235:genetics* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014018:Tissue Distribution
D003432:Cross-Linking Reagents; D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D018013:Receptors, Neuropeptide; D018017:Receptors, Pituitary Hormone-Regulating Hormone; C048250:somatotropin releasing hormone receptor