Possible involvement of p38 MAP kinase in prostaglandin E1-induced ALP activity in osteoblast-like cells.
Prostaglandins are now recognized to be important regulators for both bone formation and resorption. Among them, prostaglandin E(1) (PGE(1)) has been reported to stimulate cAMP accumulation and to induce alkaline phosphatase (ALP) activity, a marker of differentiation, in osteoblast-like cells. Recently, we have shown that p38 mitogen-activated protein (MAP) kinase pathway regulates ALP activity in response to activation of Gi protein-coupled receptors in mouse osteoblast-like MC3T3-E1 cells (Suzuki et al., Endocrinology 140 (1999) 3177). In the present study, we investigated whether p38 MAP kinase is involved in ALP activation by PGE(1) in MC3T3-E1 osteoblast-like cells. PGE(1) dose-dependently enhanced ALP activities in the concentration range between 1 nM and 1 microM in MC3T3-E1 cells. SB203580, a specific inhibitor of p38 MAP kinase, blocked the increase in ALP activity induced by PGE(1). Further analysis with western blotting suggested that PGE(1) induced an increase in tyrosine (Tyr) phosphorylation of p38 MAP kinase. Both Bt(2)cAMP, a permeable analogue of cAMP, and forskolin, which directly activates adenylate cyclase, also induced an increase in Tyr phosphorylation of p38 MAP kinase. H-89, a potent inhibitor of protein kinase A (PKA), significantly suppressed PGE(1)-induced Tyr phosphorylation of p38 MAP kinase. The results of this study suggest that PGE(1) stimulates p38 MAP kinase through the activation of PKA, resulting in the enhancement of ALP activity.
Kakita
Ayako
A
First Department of Internal Medicine, Nagoya University School of Medicine, Nagoya 466-8550, Japan.
Suzuki
Atsushi
A
Ono
Yasunaga
Y
Miura
Yoshitaka
Y
Itoh
Mitsuyasu
M
Oiso
Yutaka
Y
D000262:Adenylyl Cyclases / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000096:biosynthesis*; D000527:Alprostadil / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007093:Imidazoles; D007546:Isoquinolines; D011725:Pyridines; D013449:Sulfonamides; D005576:Colforsin; D003994:Bucladesine; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; D000262:Adenylyl Cyclases; D000527:Alprostadil; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093642:SB 203580