title: Involvement of phosphatidylcholine hydrolysis by phospholipase C in prostaglandin F2alpha-induced 1,2-diacylglycerol formation in osteoblast-like MC3T3-E1 cells.
abstract: We previously demonstrated that a prostaglandin F2alpha (PGF2alpha)-induced, sustained increase in 1,2-diacylglycerol (DAG) production was important for proliferation in osteoblast-like MC3T3-E1 cells. The 1,2-DAG formation is mediated by various enzymes, such as phos-phoinositide (PI)-specific phospholipase C (PLC), phospholipase D (PLD), and phosphatidylcholine (PC)-specific phospholipase C (PC-PLC). In the present study, to elucidate the mechanism of the 1,2-DAG formation, we have examined the PGF2alpha-induced production of [(3)H]phosphorylcholine, a product of PC-PLC activity, in [(3)H]choline-labeled MC3T3-E1 cells. The PGF2alpha-induced [(3)H]phosphorylcholine production was inhibited by genistein, a potent protein tyrosine kinase inhibitor, and increased by vanadate, a potent protein tyrosine phosphatase inhibitor. However, there were no effects after treatment with protein kinase C (PKC) inhibitors, the guanosine triphosphate (GTP) binding protein activator, NaF/AlCl(3), a Ca(2+)-ionophore, or the potent activator of PKC, phorbol 12-myristate 13-acetate (PMA), suggesting that a tyrosine kinase(s) was involved in the PGF2alpha-induced [(3)H]phosphorylcholine formation. Furthermore, a PGF2alpha analogue, 16-(3-trifluoromethylphenoxy)-Omega-tetranor-trans-Delta(2) PGF2alpha methyl ester (ONO-995), stimulated the proliferation of MC3T3-E1 cells to a level similar to that seen with PGF2alpha, and also caused phosphorylcholine and 1,2-DAG generation. However, neither an increase in intracellular free calcium ion ([Ca(2+)]i) levels by PI-PLC, nor phosphatidylethanol formation (and choline production) by PC-PLD were observed. From these results, we conclude that PGF2alpha-induced 1,2-DAG accumulation was mediated mainly via tyrosine kinase(s)-dependent PC hydrolysis by PLC activity in osteoblast-like MC3T3-E1 cells.
authors.affiliation: Department of Oral and Maxillo-Facial Surgery, Toho University School of Medicine, Tokyo, Japan. tsakai-gif@umin.ac.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sakai
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Banno
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Kato
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nozawa
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004075:Diglycerides / Q000096:biosynthesis*; D015237:Dinoprost / Q000031:analogs & derivatives / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D006868:Hydrolysis; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D013936:Thymidine; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: C011439:1,2-diacylglycerol; D004075:Diglycerides; D010713:Phosphatidylcholines; D015237:Dinoprost; D011494:Protein Kinases; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium; D013936:Thymidine