In:
Journal of Bone and Mineral Research, Wiley, Vol. 12, No. 9 ( 1997-09), p. 1348-1357
Abstract:
We have produced in yeast two human parathyroid hormone (hPTH) analogs with amino‐terminal deletions, hPTH(3–84) and hPTH(4–84), employing the mating factor α (MFα) expression system. The authenticity of the polypeptides was demonstrated by amino‐terminal analysis, amino acid composition, and molecular mass analysis. In cells (LLC‐PK 1 ) transfected with the human PTH/parathyroid hormone‐related protein (PTHrP) receptor, using [ 125 I‐Tyr 36 ]chickenPTHrP(1–36)NH 2 as radioligand, binding studies revealed dissociation constants at equilibrium ( K d ) for hPTH(3–84) and hPTH(4–84) of 4.7 and 8.0 nM, respectively, only slightly higher than natural recombinant hPTH(1–84) ( K d = 2.3 nM). In comparison, [Nle 8,18 ,Tyr 34 ]bovinePTH(3–34)NH 2 and [Tyr 36 ]cPTHrP(1–36)NH 2 showed equal K d 's of 1.9 nM. Neither of the N‐terminally deleted hPTH analogs showed any detectable stimulation of cAMP production in the cells at concentrations below 20 nM. At supersaturated concentrations (500 nM) with receptor occupancy of more than 95% these hPTH analogs revealed about 15% rest agonism compared with that of hPTH(1–84). hPTH(1–84) and [Tyr 36 ]cPTHrP(1–36)NH 2 showed an equal half maximal cyclic adenosine monophosphate (cAMP) stimulation of about 0.8 and 0.7 nM, respectively. The hPTH analogs did not show any ability to antagonize cellular cAMP production induced by either hPTH or [Tyr 36 ]cPTHrP(1–36)NH 2 . [Nle 8,18 ,Tyr 34 ]bPTH(3–34)NH 2 did also not antagonize cAMP stimulation by hPTH, but inhibited [Tyr 36 ]cPTHrP(1–36)NH 2 ‐induced cAMP production by 40% when present at a 1000 M excess. These distinct results related to PTH and PTHrP from different species are important to consider in experiments evaluating potential hPTH or PTHrP antagonism, and employment of a hPTH/PTHrP receptor model is a requirement.
Type of Medium:
Online Resource
ISSN:
0884-0431
,
1523-4681
DOI:
10.1359/jbmr.1997.12.9.1348
Language:
English
Publisher:
Wiley
Publication Date:
1997
detail.hit.zdb_id:
2008867-X
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