Parathyroid hormone-related protein(1-34) regulates Phex expression in osteoblasts through the protein kinase A pathway.
Phex (a phosphate-regulating gene with homologies to endopeptidases on the X chromosome) is expressed predominantly in bone in which it has been implicated in the mineralization process. Multiple factors and hormones, including PTHrP, regulate formation, development, and/or homeostasis of bone. The purpose of the present study was to determine whether PTHrP(1-34) regulates Phex expression and identify the signaling pathway used. Phex mRNA and protein levels were analyzed by RT-PCR and immunoblotting, respectively. In UMR-106 cells, PTHrP(1-34) caused a time- and concentration-dependent decrease in Phex expression. Forskolin, an adenylate cyclase activator, had the same effect. Dibutiryl cAMP also decreased Phex expression, and its effect was blocked by H89, a protein kinase A (PKA) inhibitor. In contrast, 12-O-tetradecanoyl phorbol-13-acetate, a protein kinase C (PKC) activator, increased Phex expression in a time- and dose-dependent manner. This effect was reversed by bisindolylmaleimide Iota, a PKC inhibitor. Bovine PTH(3-34), which activates PKC but not PKA, had no effect. On the contrary, human PTH(1-31), which activates PKA but not PKC, decreased Phex expression. H89 but not bisindolylmaleimide Iota blocked the effect of PTHrP(1-34). PTHrP(1-34) also decreased Phex expression in cultures of fetal rat calvaria cells at d 7 of culture but not at later stages. These data demonstrate that PTHrP(1-34), through PKA, down-regulates Phex expression in osteoblasts.
Vargas
Miguel Angel
MA
Département de Biochimie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada H3C 3J7.
St-Louis
Mathieu
M
Desgroseillers
Luc
L
Charli
Jean-Louis
JL
Boileau
Guy
G
D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D010006:Osteoblasts / Q000378:metabolism*; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012886:Skull / Q000166:cytology / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation
D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; D012333:RNA, Messenger; C054296:parathyroid hormone-related protein (1-34); D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; C506231:PHEX protein, human; C506229:Phex protein, rat; D013755:Tetradecanoylphorbol Acetate