Effect of prostaglandin E2 on phospholipase D activity in osteoblast-like MC3T3-E1 cells.
Recent evidence indicates that phosphatidylcholine breakdown by phospholipase D (PLD) is an important cellular control mechanism. We investigated the signaling pathway participating in prostaglandin E2 (PGE2)-induced PLD activation in osteoblast-like MC3T3-E1 cells. PGE2 stimulated PLD activity, as measured by choline generated from phosphatidylcholine, just after the stimulation. The reaction reached a plateau 15 minutes later. PGE2 stimulated PLD activity in a dose-related manner and also increased inositol phosphate (IP) formation. However, the EC50 value for PGE2-induced IP formation is lower than that for PLD activation. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a protein kinase C (PKC) activator, stimulated PLD activity, and a combination of PGE2 and TPA potentiated it in an additive manner. Although NaF, a heterotrimeric GTP-binding protein activator, significantly stimulated PLD activity, this effect was not augmented by combination with PGE2. PGE2-induced PLD activity was markedly suppressed by either chelating extracellular Ca2+ by EGTA or pertussis toxin. These findings suggest that osteoblasts might have at least two PLD activation mechanisms which involve PKC-dependent or -independent pathways. However, present results indicate that PKC is unlikely to be essential to PGE2-induced PLD activation. On the contrary, pertussis toxin-sensitive GTP-binding protein and extracellular Ca2+ might play important roles in the pathway of PGE2-induced PLD activation.
Oiso
Y
Y
First Department of Internal Medicine, Nagoya University School of Medicine, Japan.
Suzuki
A
A
Kozawa
O
O
D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D000818:Animals; D002614:Chelating Agents / Q000494:pharmacology; D002794:Choline / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010713:Phosphatidylcholines / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D012969:Sodium Fluoride / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002614:Chelating Agents; D007295:Inositol Phosphates; D010713:Phosphatidylcholines; D012969:Sodium Fluoride; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D015232:Dinoprostone; D002794:Choline; D013755:Tetradecanoylphorbol Acetate