title: Parathyroid hormone stimulation and PKA signaling of latent transforming growth factor-beta binding protein-1 (LTBP-1) mRNA expression in osteoblastic cells.
abstract: Parathyroid hormone (PTH) regulates bone remodeling and calcium homeostasis by acting on osteoblasts. Recently, the gene expression profile changes in the rat PTH (1-34, 10(-8)M)-treated rat osteoblastic osteosarcoma cell line, UMR 106-01, using DNA microarray analysis showed that mRNA for LTBP-1, a latent transforming growth factor (TGF-beta)-binding protein is stimulated by PTH. Latent TGF-beta binding proteins (LTBPs) are required for the proper folding and secretion of TGF-beta, thus modifying the activity of TGF-beta, which is a local factor necessary for bone remodeling. We show here by real time RT-PCR that PTH-stimulated LTBP-1 mRNA expression in rat and mouse preosteoblastic cells. PTH also stimulated LTBP-1 mRNA expression in all stages of rat primary osteoblastic cells but extended expression was found in differentiating osteoblasts. PTH also stimulated TGF-beta1 mRNA expression in rat primary osteoblastic cells, indicating a link between systemic and local factors for intracellular signaling in osteoblasts. An additive effect on LTBP-1 mRNA expression was found when UMR 106-01 cells were treated with PTH and TGF-beta1 together. We further examined the signaling pathways responsible for PTH-stimulated LTBP-1 and TGF-beta1 mRNA expression in UMR 106-01 cells. The PTH stimulation of LTBP-1 and TGF-beta1 mRNA expression was dependent on the PKA and the MAPK (MEK and p38 MAPK) pathways, respectively in these cells, suggesting that PTH mediates its effects on osteoblasts by several intracellular signaling pathways. Overall, we demonstrate here that PTH stimulates LTBP-1 mRNA expression in osteoblastic cells and this is PKA-dependent. This event may be important for PTH action via TGF-beta in bone remodeling.
authors.affiliation: Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Sukyee
authors.initials: S
authors.lastname: Kwok
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Nicola C
authors.initials: NC
authors.lastname: Partridge
authors.forename: Nagarajan
authors.initials: N
authors.lastname: Selvamurugan
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D053779:Latent TGF-beta Binding Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C509032:LTBP1 protein, human; D053779:Latent TGF-beta Binding Proteins; C509033:Ltbp1 protein, mouse; D010281:Parathyroid Hormone; D012333:RNA, Messenger; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases