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J Bone Miner Res

Title:		Binding and cyclic AMP stimulation by N-terminally deleted human PTHs (3-84 and 4-84) in a homologous ligand receptor system
Author(s):		Olstad OK; Reppe S; Loseth OP; Jemtland R; Gautvik KM;
Address:		"Institute of Medical Biochemistry, University of Oslo, Norway"
Journal Title:		J Bone Miner Res
Year:		1997
Volume:		12
Issue:		9
Page Number:		1348 - 1357
DOI:		10.1359/jbmr.1997.12.9.1348
ISSN/ISBN:		0884-0431 (Print) 0884-0431 (Linking)
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 alpha (MF alpha) expression system. The authenticity of the polypeptides was demonstrated by amino-terminal analysis, amino acid composition, and molecular mass analysis. In cells (LLC-PK1) transfected with the human PTH/parathyroid hormone-related protein (PTHrP) receptor, using [125I-Tyr36]chickenPTHrP(1-36)NH2 as radioligand, binding studies revealed dissociation constants at equilibrium (Kd) 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) Kd = 2.3 nM). In comparison, [Nle8,18,Tyr34]bovinePTH(3-34)NH2 and [Tyr36]cPTHrP(1-36)NH2 showed equal Kd'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 [Tyr36]cPTHrP(1-36)NH2 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 [Tyr36]cPTHrP(1-36)NH2. [Nle8,18,Tyr34]bPTH(3-34)NH2 did also not antagonize cAMP stimulation by hPTH, but inhibited [Tyr36]cPTHrP(1-36)NH2-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"
Keywords:		"Amino Acids/analysis Animals Binding, Competitive Cattle Chickens Chromatography, High Pressure Liquid Cyclic AMP/*metabolism Humans Ligands Mating Factor Models, Chemical Parathyroid Hormone/genetics/*metabolism Peptide Fragments/genetics/*metabolism Pep;"
Notes:		"MedlineOlstad, O K Reppe, S Loseth, O P Jemtland, R Gautvik, K M eng Research Support, Non-U.S. Gov't 1997/09/01 J Bone Miner Res. 1997 Sep; 12(9):1348-57. doi: 10.1359/jbmr.1997.12.9.1348"