This proposal is focused on the molecular biology of a new G protein- coupled receptor that mediates the actions of the neuroendocrine peptide growth hormone-releasing hormone (GHRH) on its target cell, the growth hormone-secreting pituitary somatotrope. Using PCR-based cloning strategies, candidate GHRH receptor cDNA clones from the pituitary gland were isolated and subsequently shown to encode a protein with seven potential membrane-spanning domains that binds to GHRH with high affinity and specificity and activates intracellular cAMP production when expressed in human or animal cell lines. The presence of a missense mutation in this GHRH receptor in the dwarf little mouse suggests an important role for GHRH and its receptor in the regulation of body growth in vertebrates. The objectives of this proposal are to identify domains within the GHRH receptor protein important for its biochemical functions in ligand binding and signal transduction, to investigate the regulation of GHRH receptor synthesis in the pituitary gland, and to establish the role of the GHRH receptor or related receptors in mediating the actions of GHRH in non- pituitary endocrine tissues. The proposed experiments are divided into four interrelated specific aims as follows: l. To elucidate the role of the cysteine-rich amino-terminal domain of the pituitary GHRH receptor in ligand recognition. 2. To determine the functional defect in the GHRH receptor protein of little mice and to assess the consequences of expressing GHRH receptor transgenes in these dwarf mice. 3. To establish the structure of the rat GHRH receptor gene and examine its expression and regulation in pituitary somatotroph cells. 4. To investigate heterogeneity in the GHRH receptor and to ascertain whether additional related receptors are expressed in GHRH-responsive non- pituitary tissues. Because of the important role played by GHRH in modulating both the proliferation and the secretory activity of pituitary somatotroph cells, an understanding of how this hormone transmits a biological signal through its receptor will be likely have direct applications to human health in the areas of pituitary tumorigenesis and disorders of growth hormone secretion and growth.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK048071-05
Application #
2684252
Study Section
Endocrinology Study Section (END)
Program Officer
Sato, Sheryl M
Project Start
1994-04-01
Project End
1999-03-31
Budget Start
1998-04-01
Budget End
1999-03-31
Support Year
5
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
City
Evanston
State
IL
Country
United States
Zip Code
60201
McElvaine, Allison T; Mayo, Kelly E (2006) A dominant-negative human growth hormone-releasing hormone (GHRH) receptor splice variant inhibits GHRH binding. Endocrinology 147:1884-94
Cunha, Shane R; Mayo, Kelly E (2002) Ghrelin and growth hormone (GH) secretagogues potentiate GH-releasing hormone (GHRH)-induced cyclic adenosine 3',5'-monophosphate production in cells expressing transfected GHRH and GH secretagogue receptors. Endocrinology 143:4570-82
Voss, T C; Goldman, L R; Seek, S L et al. (2001) GH mRNA levels are elevated by forskolin but not GH releasing hormone in GHRH receptor-expressing MtT/S somatotroph cell line. Mol Cell Endocrinol 172:125-34
Lee, E J; Kotlar, T J; Ciric, I et al. (2001) Absence of constitutively activating mutations in the GHRH receptor in GH-producing pituitary tumors. J Clin Endocrinol Metab 86:3989-95
Mayo, K E; Miller, T; DeAlmeida, V et al. (2000) Regulation of the pituitary somatotroph cell by GHRH and its receptor. Recent Prog Horm Res 55:237-66; discussion 266-7
Miller, T L; Godfrey, P A; Dealmeida, V I et al. (1999) The rat growth hormone-releasing hormone receptor gene: structure, regulation, and generation of receptor isoforms with different signaling properties. Endocrinology 140:4152-65
Gaylinn, B D; Dealmeida, V I; Lyons Jr, C E et al. (1999) The mutant growth hormone-releasing hormone (GHRH) receptor of the little mouse does not bind GHRH. Endocrinology 140:5066-74
DeAlmeida, V I; Mayo, K E (1998) Identification of binding domains of the growth hormone-releasing hormone receptor by analysis of mutant and chimeric receptor proteins. Mol Endocrinol 12:750-65
Miller, T L; Mayo, K E (1997) Glucocorticoids regulate pituitary growth hormone-releasing hormone receptor messenger ribonucleic acid expression. Endocrinology 138:2458-65