Parathyroid hormone stimulates phosphatidylethanolamine hydrolysis by phospholipase D in osteoblastic cells

Abstract

Parathyroid hormone (PTH) and phorbol-12,13-dibutyrate (PDBu) stimulate phospholipase D (PLD) activity and phosphatidylcholine (PC) hydrolysis in UMR-106 osteoblastic cells [1]. The current studies were designed to determine whether ethanolamine-containing phospholipids, and specifically phosphatidylethanolamine (PE), could also be substrates. In cells labeled with 14 Cethanolamine PTH and PDBu treatment decreased 14 C-phosphatidylethanolamine. In cells colabeled with 3 H-choline and 14 C-ethanolamine, PTH and PDBu treatment increased both 3 Hcholine and 14 C-ethanolamine release from the cells. Choline and ethanolamine phospholipid hydrolysis was increased within 5 min, and responses were sustained for at least 60 min. Maximal effects were obtained with 10 nM PTH and 50 nM PDBu. Dominant negative PLD1 and PLD2 constructs inhibited the effects of PTH on the phospholipid hydrolysis. The results suggest that both PC and PE are substrates for phospholipase D in UMR-106 osteoblastic cells and could therefore be sources of phospholipid hydrolysis products for downstream signaling in osteoblasts.

Na/H Exchange Regulatory Factor 1, a Novel AKT-associating Protein, Regulates Extracellular Signal-regulated Kinase Signaling through a B-Raf–Mediated Pathway

“…The type I parathyroid hormone (PTH), PTH/PTH-related peptide receptor (PTH1R), a member of class B of seven-transmembrane G protein-coupled receptors (GPCRs) (Horn et al, 2003) mediates PTH and PTHrP actions on extracellular calcium homeostasis and bone turnover. Although signaling through adenylyl cyclase and phospholipase C (PLC) are the best-characterized pathways, the PTH1R also signals its actions through phospholipase D and mitogen-activated protein (MAP) kinases (MAPKs) (Friedman et al, 1999;Lederer et al, 2000;Fujita et al, 2002;Radeff et al, 2004;Singh et al, 2005;Syme et al, 2005;Mahon et al, 2006;.…”

“…The type I parathyroid hormone (PTH), PTH/PTH-related peptide receptor (PTH1R), a member of class B of seven-transmembrane G protein-coupled receptors (GPCRs) (Horn et al, 2003) mediates PTH and PTHrP actions on extracellular calcium homeostasis and bone turnover. Although signaling through adenylyl cyclase and phospholipase C (PLC) are the best-characterized pathways, the PTH1R also signals its actions through phospholipase D and mitogen-activated protein (MAP) kinases (MAPKs) (Friedman et al, 1999;Lederer et al, 2000;Fujita et al, 2002;Radeff et al, 2004;Singh et al, 2005;Syme et al, 2005;Mahon et al, 2006;.MAPKs are protein serine and threonine kinases that play important roles in cell growth, differentiation, survival, and in many aspects of bone turnover and calcium balance (Ishizuya et al, 1997;Sneddon et al, 2000;Fujita et al, 2002;Ahmed et al, 2003;Schindeler and Little, 2006). Extracellular signalregulated kinases (ERKs) 1 and 2, c-Jun-NH 2 -terminal kinase, and p38 kinase lie at the end of parallel MAPK cascades (Cobb, 1999).…”

Phospholipases of Mineralization Competent Cells and Matrix Vesicles: Roles in Physiological and Pathological Mineralizations

“…More information on possible functional roles of PLD is gained from osteoblast-like UMR-106 cells. A phorbol 12-myristate 13-acetate treatment of osteoblast-like UMR-106 cells activated PLD and lead to the production of PGE 2 but not PGF 2 α [604] confirming for the first time that in osteoblasts, PA can be converted in PGE 2 via a PLD/phosphatidate phosphohydrolase/DAG lipase/COX pathway [605–607]. Arachidonate metabolites such as PGE 2 were found to play an important role in bone and cartilage metabolism [608].…”

“…For example, PTH stimulates bone formation by preventing osteoblast apoptosis [609] and by activating diverse signaling pathways. PTH can stimulate PLD activity in UMR-106 cells [605–607]. Another example is provided by epidermal growth factor (EGF) which participates in the regulation of bone resorption in mice and mouse calvaria in vitro organ cultures [610].…”

Effects of phospholipase D during cultured osteoblast mineralization and bone formation

“…A glycophosphatidylinositol-specific PLD is also expressed during the process of bone formation in mouse embryogenesis. 12,13 Furthermore, MG63 human osteosarcoma cells exhibit increased PLD activity during differentiation on titanium biomaterial. 11 Since then, a controlled regulation of PLD activity has been observed in other bone cells.…”