The extracellular amino-terminal region of the parathyroid hormone (PTH)/PTH-related peptide receptor determines the binding affinity for carboxyl-terminal fragments of PTH-(1-34)

• Published in: Endocrinology (Philadelphia) Vol. 134; no. 2; p. 879
• Main Authors: Jüppner, H, Schipani, E, Bringhurst, F R, McClure, I, Keutmann, H T, Potts, Jr, J T, Kronenberg, H M, Abou-Samra, A B, Segre, G V, Gardella, T J
• Format: Journal Article
• Language: English
• Published: United States 01-02-1994
• Subjects: Animals; Binding Sites; Cattle; Cell Line; Cercopithecus aethiops; Gene Expression; Humans; Kidney; Kinetics; Mutagenesis, Site-Directed; Parathyroid Hormone - metabolism; Parathyroid Hormone-Related Protein; Peptide Fragments - metabolism; Protein Conformation; Protein Sorting Signals - chemistry; Protein Sorting Signals - metabolism; Protein Structure, Secondary; Proteins - metabolism; Rats; Receptor, Parathyroid Hormone, Type 1; Receptors, Parathyroid Hormone - chemistry; Receptors, Parathyroid Hormone - metabolism; Recombinant Proteins - metabolism; Restriction Mapping; Teriparatide; Transfection
• ISSN: 0013-7227
• DOI: 10.1210/en.134.2.879

The recombinant human PTH/PTH-related peptide (PTHrP) receptor, when transiently expressed in COS-7 cells, binds [Nle8,18,Tyr34] bovine PTH-(7-34)amide [PTH-(7-34)], human PTH-(10-34)amide [PTH-(10-34)], and bovine PTH-(15-34)amide [PTH-(15-34)] with at least 50-fold higher affinity than does the rat receptor homolog. In contrast, PTH-(1-34) binding affinities are similar for both receptor homologs. To map those areas of the PTH/PTHrP receptors that determine the binding specificity for carboxyl-terminal fragments of PTH-(1-34), we constructed chimeric rat/human PTH/PTHrP receptors. These bound PTH-(1-34) with normal affinity and, therefore, must have an overall conformation that resembles that of native receptors. Chimeras with the amino-terminal extracellular domain of the human PTH/PTHrP receptor have a considerably higher binding affinity for PTH-(7-34), PTH-(10-34), and PTH-(15-34) than do the reciprocal receptor constructs in which the amino-terminal region is from the rat PTH/PTHrP receptor. The opossum PTH/PTHrP receptor homolog also binds PTH-(7-34) with higher affinity than the rat receptor, and studies of rat/opossum chimeras confirm the importance of the amino-terminal extracellular domain in determining the PTH-(7-34) binding specificity. Mutant rat and human PTH/PTHrP receptors in which either residues 61-105 of the extracellular region or most of the intracellular tail were deleted have PTH-(7-34) binding characteristics indistinguishable from those of either wild-type receptor. These findings indicate that the amino-terminal extracellular region of the PTH/PTHrP receptor contains a domain(s) that largely determines the binding affinity of amino-terminally truncated PTH analogs. This region, therefore, is likely to constitute a site for ligand-receptor interaction.