Transcriptional regulation of osteopontin production in rat osteoblast-like cells by parathyroid hormone.
Osteopontin (OP) or bone sialoprotein is a recently characterized extracellular matrix protein which is abundant in bone and is produced by osteoblasts. Parathyroid hormone (PTH) is a potent calcitropic hormone which regulates osteoblastic function including the synthesis of extracellular matrix proteins. This study examines the effect of human PTH (hPTH-[1-34]) on the expression of this novel protein in rat osteoblast-like cells. hPTH(1-34) significantly decreased the amount of OP in culture media of the rat osteoblastic osteosarcoma cell line, ROS 17/2.8, detected by Western immunoblot analysis. hPTH(1-34) also suppressed the steady-state level of OP mRNA two- to threefold with an ED50 of approximately 3 X 10(-10) M. This inhibition was detectable at 24 h, reached its nadir at 48 h, and lasted at least up to 96 h. The hPTH(1-34) effects were mimicked by isobutylmethylxanthine, cholera toxin, 8-bromo-cAMP, forskolin, and isoproterenol. hPTH(1-34) suppressed by two- to threefold the rate of OP gene transcription, estimated by nuclear run-on assays. The suppression of OP mRNA levels by hPTH(1-34) was also seen when basal levels were increased by transforming growth factor type beta, or 1,25-dihydroxyvitamin D3, or were decreased by dexamethasone. A similar decrease in the steady-state level of OP mRNA by hPTH(1-34) was also observed in primary cultures of osteoblast-enriched cells from fetal rat calvaria. These findings indicate that hPTH(1-34) suppresses the production of the novel extracellular matrix protein, OP, in osteoblasts at least in part through transcriptional control.
Noda
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M
Department of Bone Biology and Osteoporosis Research, Merck, Sharp, & Dohme Research Laboratories, West Point, Pennsylvania 19486.
Rodan
G A
GA
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002117:Calcitriol / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D010006:Osteoblasts / Q000378:metabolism*; D053495:Osteopontin; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics; D019379:Teriparatide; D014158:Transcription, Genetic / Q000187:drug effects*; D015291:Transforming Growth Factors / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012333:RNA, Messenger; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506897:Spp1 protein, rat; D053495:Osteopontin; D019379:Teriparatide; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D015291:Transforming Growth Factors; D003907:Dexamethasone; D002772:Cholera Toxin; D002117:Calcitriol; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine