Inhibition of PI3K/p70 S6K and p38 MAPK cascades increases osteoblastic differentiation induced by BMP‐2

Abstract

Bone morphogenetic proteins (BMPs) transdifferentiate C2C12 cells from the myogenic to the osteogenic lineage. In this work we examine the role of the phosphatidylinositol 3-kinase/p70 S6 kinase (PI3K/p70 S6K) and p38 mitogen-activated protein kinase (p38 MAPK) cascades in the osteogenic effects of BMP-2. BMP-2 stimulated both cascades transiently (maximal at 1 h and decreasing thereafter). In contrast, BMP-2 had no effect on p42/p44 MAPK (Erks) stimulation. We also analyzed the effects of selective inhibitors of these pathways on the expression of osteogenic markers. Inhibitors of p38 MAPK (SB203580) or the PI3K/p70 S6K pathway (Ly294002 and rapamycin) not only fail to block the osteoblast phenotype induced by BMP-2, measured as induction of Cbfa1 expression and transcriptional activity, but also potentiate the effect of BMP-2 on late osteoblast markers, such as alkaline phosphatase activity and osteocalcin expression. These data suggest that, in contrast to their positive effect on myogenic differentiation, PI3K/p70 S6K and p38 MAPK cascades have a negative role in osteoblast differentiation. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

c-Jun N-terminal kinase 1 negatively regulates osteoblastic differentiation induced by BMP2 via phosphorylation of Runx2 at Ser104

“…In addition, BMP2 promotes osteoblastic differentiation in several cell types, such as multipotent myoblastic C2C12 cells, preosteoblastic MC3T3-E1 cells, primary calvarial osteoblasts, and bone marrow stromal cells. (9,21,30) BMP2 has been reported to activate ERK and p38 MAP kinases in the multipotent C2C12 cells, (11,38) and mainly activates JNK and p38 MAP kinases in MC3T3-E1 cells. (13) A previous study mentioned that JNK2 is mainly activated in the presence of osteogenic supplements (ascorbic acid, b-glycerophosphate, and dexamethasone).…”

Filamin B Plays a Key Role in Vascular Endothelial Growth Factor-induced Endothelial Cell Motility through Its Interaction with Rac-1 and Vav-2

“…Western blotting was performed as described (26). The blots were incubated with polyclonal rabbit anti-filamin B antibody (17) …”

“…Total RNA from cells was extracted using the phenol/chloroform method, and Northern blotting using 20 g of RNA was performed as described (26). Blots were hybridized to mouse filamin B cDNA, to a fragment of the 3Ј-end of the human filamin A sequence (a generous gift from Dr. Saret (National Institutes of Health)) or to rat glyceraldehyde-3-phosphate dehydrogenase cDNA labeled with [␣-32 P]dCTP (Amersham Biosciences).…”

Effect of Insulin-like Growth Factor-1 on Bone Morphogenetic Protein-2 Expression in Hepatic Carcinoma SMMC7721 Cells through the p38 MAPK Signaling Pathway

“…Many physiological functions of BMP-2 are realized after the MAPK and P13K pathways are activated (Vinals et al, 2002;Guicheux et al, 2003). BMP-2 binds to BMPR-I and BMPR-II to form receptor compounds; these compounds promote the phosphorylation of Smad-1/5/8 to transmit cellular signals, thus, to regulate the target gene (Nishimura et al, 1998).…”