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).
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.
Jüppner
H
H
Department of Pediatrics, Massachusetts General Hospital, Boston.
Schipani
E
E
Bringhurst
F R
FR
McClure
I
I
Keutmann
H T
HT
Potts
J T
JT
Kronenberg
H M
HM
Abou-Samra
A B
AB
Segre
G V
GV
Gardella
T J
TJ
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002460:Cell Line; D002522:Chlorocebus aethiops; D015870:Gene Expression; D006801:Humans; D007668:Kidney; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010281:Parathyroid Hormone / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000378:metabolism*; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D019379:Teriparatide; D014162:Transfection
C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D011506:Proteins; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone; D011994:Recombinant Proteins; D019379:Teriparatide