title: Structural modifications of non-mammalian gonadotropin-releasing hormone (GnRH) isoforms: design of novel GnRH analogues.
abstract: Three natural forms of vertebrate gonadotropin-releasing hormone (GnRH) provided the structural basis upon which to design new GnRH agonists: [His5,Trp7,Leu8]-GnRH, dogfish (df) GnRH; [His5,Asn8]-GnRH, catfish (cf) GnRH; and [His5,Trp7,Tyr8]-GnRH, chicken (c) GnRH-II. The synthetic peptides incorporated the position 6 dextro (D)-isomers D-arginine (D-Arg) or D-naphthylalanine (D-Nal) in combination with an ethylamide substitution of position 10. The in vitro potencies for LH and FSH release of these analogues were assessed using static cultures of rat anterior pituitary cells. Efficacious peptides were examined for their gonadotropin-II and growth hormone releasing abilities from perifused goldfish pituitary fragments. Rat LH and FSH release was measured using homologous radioimmunoassays, whereas goldfish growth hormone and gonadotropin-II release were determined using heterologous carp hormone radioimmunoassays. The receptor binding of the most potent analogues was determined in bovine pituitary membrane preparations. Substitution of D-Nal6 into [His5,Asn8]-GnRH increased the potency over 2200-fold compared with the native ligand (cfGnRH) in cultured rat pituitary cells. This was equivalent to a 55-fold greater potency than that of the native mammal (m) GnRH peptide. Substitution of D-Nal6 or D-Arg6 into dfGnRH or cGnRH-II resulted in potencies that were related to the overall hydrophobicity of the analogues. The [D-Nal6,Pro9NEt]-cfGnRH bound to the bovine membrane preparation with an affinity statistically similar to that of [D-Nal6,Pro9NEt]-mGnRH (kd = 0.40 +/- 0.04 and 0.55 +/- 0.10 nM, respectively) in cultured rat pituitary cells. All analogues tested released the same ratio of FSH to LH. In goldfish, the analogues did not possess superagonistic activity but instead desensitized the pituitary fragments at lower analogue doses than that of the sGnRH standard suggesting differences in receptor affinity or signal transduction.
authors: Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, CA 92037, USA.
authors: D A
authors: DA
authors: Lovejoy
authors: A Z
authors: AZ
authors: Corrigan
authors: C S
authors: CS
authors: Nahorniak
authors: M H
authors: MH
authors: Perrin
authors: J
authors: J
authors: Porter
authors: R
authors: R
authors: Kaiser
authors: C
authors: C
authors: Miller
authors: D
authors: D
authors: Pantoja
authors: A G
authors: AG
authors: Craig
authors: R E
authors: RE
authors: Peter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000737:chemistry*; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013329:Structure-Activity Relationship
chemical_list: D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone