Involvement of amino acids flanking Glu7.32 of the gonadotropin-releasing hormone receptor in the selectivity of antagonists.
The Glu/Asp(7.32) residue in extracellular loop 3 of the mammalian type-I gonadotropin-releasing hormone receptor (GnRHR) interacts with Arg(8) of GnRH-I, conferring preferential ligand selectivity for GnRH-I over GnRH-II. Previously, we demonstrated that the residues (Ser and Pro) flanking Glu/Asp(7.32) also play a role in the differential agonist selectivity of mammalian and non-mammalian GnRHRs. In this study, we examined the differential antagonist selectivity of wild type and mutant GnRHRs in which the Ser and Pro residues were changed. Cetrorelix, a GnRH-I antagonist, and Trptorelix-2, a GnRH-II antagonist, exhibited high selectivity for mammalian type-I and non-mammalian GnRHRs, respectively. The inhibitory activities of the antagonists were dependent on agonist concentration and subtype. Rat GnRHR in which the Ser-Glu-Pro (SEP) motif was changed to Pro-Glu-Val (PEV) or Pro-Glu-Ser (PES) had increased sensitivity to Trptorelix-2 but decreased sensitivity to Cetrorelix. Mutant bullfrog GnRHR-1 with the SEP motif had the reverse antagonist selectivity, with reduced sensitivity to Trptorelix-2 but increased sensitivity to Cetrorelix. These findings indicate that the residues flanking Glu(7.32) are important for antagonist as well as agonist selectivity.
Wang
Chengbing
C
Graduate School of Medicine, Korea University, Seoul 136-705, Korea.
Oh
Da Young
DY
Maiti
Kaushik
K
Kwon
Hyuk Bang
HB
Cheon
Jun
J
Hwang
Jong-Ik
JI
Seong
Jae Young
JY
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D006727:Hormone Antagonists / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D051381:Rats; D011966:Receptors, LHRH / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D006727:Hormone Antagonists; D009842:Oligopeptides; D011966:Receptors, LHRH; C529370:acetyl-(2-naphthyl)alanyl-4-chlorophenylalanyl-3-(3-pyridinyl)alanyl-seryl-histidyl-n5-aminocarbonylornithyl-tryptophyl-tyrosyl-prolyl-alaninamide; D007987:Gonadotropin-Releasing Hormone; D018698:Glutamic Acid; C062876:cetrorelix