Abstract
Bone morphogenetic protein (BMP)-2, a member of the transforming growth factor-beta (TGF-beta) superfamily, is able to induce osteoblastic differentiation of C2C12 cells. Both Smad and mitogen-activated protein kinase (MAPK) pathways are essential components of the TGF-beta superfamily signaling machinery. Although Smads have been demonstrated to participate in the BMP-2-induced osteoblastic differentiation of C2C12 cells, the role of MAPK has not been addressed. This report shows that BMP-2 activates ERK and p38, but not JNK, in C2C12 cells. Pretreatment of cells with the p38 inhibitor, SB203580, dramatically reduced BMP-2-induced expression of the osteoblast markers alkaline phosphatase (ALP) and osteocalcin (OC). Nevertheless, overexpression of MKK3, a protein kinase that phosphorylates and activates p38, failed to induce ALP or OC expression in the absence of BMP-2, indicating that p38 activation is necessary but not sufficient for the acquisition of the osteoblast phenotype by these cells. Although ALP induction was increased slightly in the presence of PD-98059, a selective inhibitor of the ERK cascade, this compound significantly inhibited both steady-state and BMP-2-induced OC RNA levels. Our results indicate that p38 and ERK cascades play a crucial role in the osteoblast differentiation of C2C12 cells mediated by BMP-2.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alkaline Phosphatase / genetics
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Animals
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Bone Development / drug effects*
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Bone Development / physiology
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins / metabolism
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Bone Morphogenetic Proteins / pharmacology*
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Cell Differentiation / drug effects*
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Cell Differentiation / physiology
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Cells, Cultured / cytology
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Cells, Cultured / drug effects*
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Cells, Cultured / metabolism
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Cricetinae
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Enzyme Inhibitors / pharmacology
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Female
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Flavonoids
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Gene Expression Regulation, Enzymologic / drug effects
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Gene Expression Regulation, Enzymologic / physiology
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Imidazoles / pharmacology
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MAP Kinase Kinase 3
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MAP Kinase Signaling System / drug effects*
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MAP Kinase Signaling System / physiology
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Mice
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Mitogen-Activated Protein Kinase 8
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Mitogen-Activated Protein Kinase Kinases / genetics
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Mitogen-Activated Protein Kinases / drug effects
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Mitogen-Activated Protein Kinases / metabolism
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Osteoblasts / cytology
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Osteoblasts / drug effects*
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Osteoblasts / metabolism
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Osteocalcin / genetics
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Protein-Tyrosine Kinases / genetics
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Pyridines / pharmacology
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RNA, Messenger / drug effects
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RNA, Messenger / metabolism
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Stem Cells / cytology
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Stem Cells / drug effects*
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Stem Cells / metabolism
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Transforming Growth Factor beta*
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p38 Mitogen-Activated Protein Kinases
Substances
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Bmp2 protein, mouse
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins
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Enzyme Inhibitors
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Flavonoids
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Imidazoles
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Pyridines
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RNA, Messenger
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Transforming Growth Factor beta
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Osteocalcin
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Protein-Tyrosine Kinases
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Mitogen-Activated Protein Kinase 8
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Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 3
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Map2k3 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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Alkaline Phosphatase
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SB 203580
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one