Structure and regulation of the growth hormone secretagogue receptor.

Synthetic growth hormone secretagogues (GHS) stimulate growth hormone release through binding to a recently cloned specific growth hormone secretagogue receptor (GHS-R). Ghrelin, the endogenous ligand of this receptor, is part of a new endocrine pathway controlling GH secretion. However, the major physiological function of the ghrelin/GHS-R system may be related to the control of energy homeostasis. The GHS-R belongs to the family of G-protein coupled receptors. Two different receptor variants type 1a and 1b have been described which differ in their carboxyl-terminal amino acids. Both types are encoded by a single gene of approximately 4.3 kb in length through different processing. The promoter region of the human GHS-R was recently characterized. Analysis of the GHS-R may lead to new insights into the control of GH secretion and additional physiological roles of ghrelin. This review will summarize data regarding the structure of the GHS-R gene and the protein encoded, reports investigating the expression and control of the GHS-R in various tissues, and studies of the underlying transcriptional mechanisms.