Nucleotide regulation of growth hormone-releasing factor binding to rat pituitary receptors.
The specific binding of a GRF radioligand, [His1,125I-Tyr10,Nle27]hGRF-1-32NH2, to rat pituitary homogenates is reduced by the addition of GTP and its nonhydrolyzable analogs 5'-guanylylimidodiphosphate (GppNHp) and guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S). GDP and cAMP had no effect while the nonhydrolyzable ATP analogs 5'-adenylylimidodiphosphate and adenosine 5'-O-(3-thiotriphosphate) did elicit a significant reduction in GRF binding. The effect of GppNHp was half-maximal at 0.2 microM, and the maximum inhibition achieved was 85%. The effect of 0.1 microM GppNHp on GRF competitive displacement experiments indicated a significant reduction in affinity for the ligand (Kd = 0.51 +/- 0.11 nM in the absence of GppNHp and 2.1 +/- 1.1 nM in its presence) without an effect on receptor number. The GRF radioligand dissociates slowly from its receptor (t1/2 = 250 +/- 50 min), but the addition of 0.1 microM GppNHp converts approximately half of the receptors present to a more rapidly dissociating form (t1/2 = 9 +/- 10 min). These results are consistent with existing models for receptor-G-protein interactions, and thus, we conclude that transduction of the GRF response across the cell membrane involves a guanine nucleotide-binding protein, presumably Gs.
Struthers
R S
RS
Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, California 92037.
Perrin
M H
MH
Vale
W
W
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009711:Nucleotides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018013:Receptors, Neuropeptide; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013873:Thionucleotides / Q000494:pharmacology
D009711:Nucleotides; D018013:Receptors, Neuropeptide; D017981:Receptors, Neurotransmitter; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013873:Thionucleotides; D000266:Adenylyl Imidodiphosphate; D006165:Guanylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C022570:adenosine 5'-O-(2-thiotriphosphate); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D013007:Growth Hormone-Releasing Hormone; C045741:somatotropin releasing hormone (1-32)amide, His(1)-I-Tyr(10)-Nle(27)-; D000242:Cyclic AMP; C048250:somatotropin releasing hormone receptor