Vol. 274, Issue 2, E297-E303, February 1998
New insights into interactions between the human PTH/PTHrP
receptor and agonist/antagonist binding
Shoichi
Fukayama1,
Miryam
Royo5,
Masahiko
Sugita4,
Amy
Imrich2,
Michael
Chorev5,
Larry J.
Suva5,
Michael
Rosenblatt5, and
Armen H.
Tashjian Jr.1,3
1 Department of Molecular and
Cellular Toxicology; 2 Program in
Physiology, Department of Environmental Health, Harvard School of
Public Health, 3 Department of
Biological Chemistry and Molecular Pharmacology, Harvard Medical
School; 4 Lymphocyte Biology
Section, Division of Rheumatology and Immunology, Brigham and
Women's Hospital, Harvard Medical School, and
5 Division of Bone and Mineral
Metabolism, Harvard-Thorndike and Charles A. Dana Laboratories,
Department of Medicine, Beth Israel Deaconess Medical Center,
Harvard Medical School, Boston, MA 02115
We prepared a
polyclonal antiserum [Ab-(88
97)] against residues
88-97 of the NH2-terminal
tail of the human (h) parathyroid hormone (PTH)/PTH-related protein
(PTHrP) receptor. Ab-(8897) bound specifically to the receptor, as
assessed by fluorescence-activated cell sorter analysis of HEK C21
cells, which stably express ~400,000 hPTH/PTHrP receptors per cell.
Unlike PTH, Ab-(8897) binding did not elicit either adenosine
3',5'-cyclic monophosphate or intracellular calcium
concentration signaling responses in these cells. Incubation of C21
cells for 90 min at 4°C with hPTH-(134) plus antiserum reduced
the Ab-(8897) binding to the cells by up to 40-50% of control
values in a PTH concentration-dependent fashion with a half-maximal
effective concentration of ~5 nM. The decrease in Ab-(8897) binding
caused by hPTH-(134) was completely reversed by coincubation with
hPTHrP-(734). We conclude that residues 88-97 of the hPTH/PTHrPR
are involved, either directly or indirectly, in agonist but not
antagonist binding to the receptor.
parathyroid hormone/parathyroid hormone-related protein receptor
antibody; agonist; antagonist
