Agonist and receptor binding properties of adrenocorticotropin peptides using the cloned mouse adrenocorticotropin receptor expressed in a stably transfected HeLa cell line.
The cloned mouse ACTH receptor was expressed in stably transfected human HeLa cells that lack an endogenous melanocortin receptor. ACTH[1-39] and several N- and C-terminally truncated analogues of ACTH were studied for their ability to stimulate cAMP generation and to displace bound 125I-ACTH. Only three of the peptides tested, ACTH[1-24], ACTH[1-39], and ACTH[1-17] were found to have agonist activity with EC50 values of 7.5, 57, and 49 x 10(-12) M respectively. Two peptides, ACTH[11-24] and ACTH[7-39], were devoid of agonist activity but had substantial competitive antagonist activity with IC50 values of approximately 10(-9) M. In binding studies, ACTH[1-39] and ACTH[1-24] were able to fully displace bound ligand, and Scatchard analysis indicated a dissociation constant (KD) of 0.84 and 0.94 x 10(-9) M for the two peptides, respectively. ACTH[1-17], ACTH[11-24], and ACTH[7-39] were only capable of displacing 60-70% of bound ligand. A three-site model for the interaction of ACTH and its receptor is proposed on the basis of these findings.
Kapas
S
S
Department of Chemical Endocrinology, St. Bartholomew's Hospital Medical College, West Smithfield, London, United Kingdom.
Cammas
F M
FM
Hinson
J P
JP
Clark
A J
AJ
D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000096:biosynthesis; D006367:HeLa Cells; D006801:Humans; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism*; D018043:Receptors, Corticotropin / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D010446:Peptide Fragments; D018043:Receptors, Corticotropin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP