Parathyroid hormone increases beta-catenin levels through Smad3 in mouse osteoblastic cells.
PTH, via the PTH/PTH-related protein receptor type 1 that couples to both protein kinase A (PKA) and protein kinase C (PKC) pathways, and the canonical Wnt-beta-catenin signaling pathway play important roles in bone formation. In the present study we have examined the interaction between the PTH and Wnt signaling pathways in mouse osteoblastic MC3T3-E1 cells. PTH dose- and time-dependently increased the concentrations of beta-catenin. The PKA activator, forskolin, and the PKC activator, phorbol 12-myristate-13-acetate, as well as the PTH analog, [Nle(8,18),Tyr(34)]human PTH-(3-34)amide, all increased beta-catenin levels. Both H-89, a specific PKA inhibitor, and PKC inhibitors, staurosporine and calphostin C, antagonized PTH stimulation of beta-catenin levels. TGF-beta as well as transfection of the TGF-beta-signaling molecule, Smad3, enhanced beta-catenin levels, and this was antagonized by transfection of a dominant-negative Smad3. The transcriptional activity of transfected dominant-active beta-catenin was enhanced by PTH, an effect that was antagonized by cotransfection of a dominant-negative Smad3. PTH as well as LiCl(2), which mimics the effects of the Wnt-beta-catenin pathway, rescued the dexamethasone- and etoposide-induced apoptosis of osteoblastic cells. In conclusion, the data demonstrate that PTH stimulates osteoblast beta-catenin levels via Smad3, and that both PKA and PKC pathways are involved. The canonical Wnt-beta-catenin pathway is likely to be involved in the antiapoptotic actions of PTH by acting through Smad3 in osteoblasts.
Division of Endocrinology/Metabolism, Neurology, and Hematology/Oncology, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, Chuo-ku, Japan.
Takako
T
Tobimatsu
Hiroshi
H
Kaji
Hideaki
H
Sowa
Junko
J
Naito
Lucie
L
Canaff
Geoffrey N
GN
Hendy
Toshitsugu
T
Sugimoto
Kazuo
K
Chihara
D000818:Animals; D017209:Apoptosis; D001846:Bone Development; D001842:Bone and Bones / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation; D007546:Isoquinolines / Q000494:pharmacology; D018021:Lithium Chloride / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D009281:Naphthalenes / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000378:metabolism / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051900:Smad3 Protein / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007546:Isoquinolines; D009281:Naphthalenes; D010281:Parathyroid Hormone; D051900:Smad3 Protein; D013449:Sulfonamides; D016212:Transforming Growth Factor beta; D051176:beta Catenin; D005047:Etoposide; D003907:Dexamethasone; D008156:Luciferases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D018021:Lithium Chloride; D019311:Staurosporine; C058819:calphostin C; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D013755:Tetradecanoylphorbol Acetate