Journal
JOURNAL OF CELLULAR BIOCHEMISTRY
Volume 84, Issue 3, Pages 583-589Publisher
WILEY
DOI: 10.1002/jcb.10056
Keywords
BMP; osteocalcin; MAP kinase; osteoblast
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In the present study, we investigated whether the mitogen-activated protein (MAP) kinase superfamily is involved in the bone morphogenetic protein (BMP)-4-stimulated synthesis of osteocalcin in osteoblast-like MC3T3-E1 cells. BMP-4 dose-dependently stimulated osteocalcin synthesis. BMP-4 markedly induced the phosphorylation of p44/p42 MAP kinase and p38 MAP kinase, while having little effect on SAPK (stress-activated protein kinase)/JNK (c-Jun N terminal kinase) phosphorylation. SB203580 and PD169316, specific inhibitors of p38 MAP kinase, significantly reduced the osteocalcin synthesis stimulated by BMP-4. In contrast, PD98059 and U0126, inhibitors of upstream kinase of p44/p42 MAP kinase, markedly enhanced the BMP-4-stimulated osteocalcin synthesis. The BMP-4-induced phosphorylation of p44/p42 MAP kinase was suppressed by PD98059, which did not, however, affect the BMP-4-induced phosphorylation of p38 MAP kinase. Taken together, our results strongly suggest that p38 MAP kinase takes part in BMP-4-stimulated osteocalcin synthesis as a positive regulator in osteoblasts, whereas p44/p42 MAP kinase acts as a negative regulator in the synthesis. (C) 2001 Wiley-Liss, Inc.
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