CDB15:0000721 GNRH2 — GNRHR
Experimentally validated in Human; Orthology-inferred in Zebrafish, Macaque, Pig, Cow, Chimp, Horse, Marmoset
Title
Journal:; Year Published:
Abstract
Identification of a novel ligand binding residue Arg38(1.35) in the human gonadotropin-releasing hormone receptor.
Molecular pharmacology, 2008; PubMed, Homo sapiens GNRH2 — Homo sapiens GNRHR
ABSTRACT: Delineation of peptide ligand binding sites is of fundamental importance in rational drug design and in understanding ligand-induced receptor activation. Molecular modeling and ligand docking to previously experimentally identified binding sites revealed a putative novel interaction between the C terminus of gonadotropin-releasing hormone (GnRH) and Arg(38(1.35)), located at the extracellular end of transmembrane domain 1 of the human GnRH receptor. Mutation of Arg(38(1.35)) to alanine resulted in 989- and 1268-fold reduction in affinity for GnRH I and GnRH II, respectively, the two endogenous ligands. Conservative mutation of Arg(38(1.35)) to lysine had less effect, giving reduced affinities of GnRH I and GnRH II by 24- and 54-fold, respectively. To test whether Arg(38(1.35)) interacts with the C-terminal Gly(10)-NH(2) of GnRH, binding of GnRH analogs with substitution of the C-terminal glycinamide with ethylamide ([Pro(9)-NHEt]GnRH) was studied with wild-type and Arg(38(1.35)) mutant receptors. Mutation of Arg(38(1.35)) to lysine or alanine had much smaller effect on receptor affinity for [Pro(9)-NHEt]GnRH analogs and no effect on binding affinity of peptide antagonist cetrorelix. In parallel with the decreased affinity, the mutants also gave a decreased potency to GnRH-elicited inositol phosphate (IP) responses. The mutant receptors had effects on [Pro(9)-NHEt]GnRH-elicited IP responses similar to that of the parent GnRHs. These findings indicate that Arg(38(1.35)) of the GnRH receptor is essential for high-affinity binding of GnRH agonists and stabilizing the receptor active conformation. The mutagenesis results support the prediction of molecular modeling that Arg(38(1.35)) interacts with the C-terminal glycinamide and probably forms hydrogen bonds with the backbone carbonyl of Pro(9) and Gly(10)-NH(2).
GnRH-II antagonists induce apoptosis in human endometrial, ovarian, and breast cancer cells via activation of stress-induced MAPKs p38 and JNK and proapoptotic protein Bax.
Cancer research, 2009; PubMed, Homo sapiens GNRH2 — Homo sapiens GNRHR
ABSTRACT: Recently, we could show that gonadotropin-releasing hormone (GnRH)-II antagonists induce apoptosis in human endometrial, ovarian, and breast cancer cells in vitro and in vivo. In the present study, we have ascertained receptor binding and effects of GnRH-II antagonists on mitogenic signal transduction and on activation of proapoptotic protein Bax. The GnRH-II antagonists tested showed EC50 values for GnRH-I receptor binding in the range of 1 to 2 nmol/L. The GnRH-II agonist [D-Lys6]GnRH-II showed an EC50 value for GnRH-I receptor binding of approximately 1,000 nmol/L. Agonistic activity on GnRH-I receptor function with an EC50 of 13 nmol/L has been determined for [D-Lys6]GnRH-II. Antagonistic activities with EC50 values in the range of 1 nmol/L were determined for the GnRH-II antagonists. Treatment of human endometrial, ovarian, and breast cancer cells with GnRH-II antagonists resulted in time-dependent activation of stress-induced mitogen-activated protein kinases p38 and c-Jun NH2-terminal kinase. In addition, treatment with GnRH-II antagonists induced time-dependent activation of proapoptotic protein Bax. GnRH-II antagonists are not involved in activation of protein kinase B/Akt or extracellular signal-regulated kinase 1/2. The GnRH-II antagonists tested had similar binding affinities to the GnRH-I receptor comparable with that of GnRH-I antagonist Cetrorelix. Referring to the cyclic AMP response element reporter gene activation assay, the GnRH-II agonist [D-Lys6]GnRH-II has to be classified as an agonist at the GnRH-I receptor, whereas the GnRH-II antagonists tested are clear antagonists at the GnRH-I receptor. GnRH-II antagonists induce apoptotic cell death in human endometrial, ovarian, and breast cancer cells via activation of stress-induced mitogen-activated protein kinases p38 and c-Jun NH2-terminal kinase followed by activation of proapoptotic protein Bax.