BMP2-induced apoptosis is mediated by activation of the TAK1-p38 kinase pathway that is negatively regulated by Smad6.
Bone morphogenetic protein 2 (BMP2), a member of the transforming growth factor-beta (TGF-beta) superfamily, regulates a variety of cell fates and functions. At present, the molecular mechanism by which BMP2 induces apoptosis has not been fully elucidated. Here we propose a BMP2 signaling pathway that mediates apoptosis in mouse hybridoma ... MH60 cells whose growth is interleukin-6 (IL-6)-dependent. BMP2 dose-dependently induces apoptosis in MH60 cells even in the presence of IL-6. BMP2 has no inhibitory effect on the IL-6-induced tyrosine phosphorylation of STAT3, and the bcl-2 gene expression which is known to be regulated by STAT3, suggesting that BMP2-induced apoptosis is not attributed to alteration of the IL-6-mediated bcl-2 pathway. We demonstrate that BMP2 induces activation of TGF-beta-activated kinase (TAK1) and subsequent phosphorylation of p38 stress-activated protein kinase. In addition, forced expression of kinase-negative TAK1 in MH60 cells blocks BMP2-induced apoptosis. These results indicate that BMP2-induced apoptosis is mediated through the TAK1-p38 pathway in MH60 cells. We also show that MH60-derived transfectants expressing Smad6 are resistant to the apoptotic signal of BMP2. Interestingly, this ectopic expression of Smad6 blocks BMP2-induced TAK1 activation and p38 phosphorylation. Moreover, Smad6 can directly bind to TAK1. These findings suggest that Smad6 is likely to function as a negative regulator of the TAK1 pathway in the BMP2 signaling, in addition to the previously reported Smad pathway.
Mesh Terms:
Animals, Apoptosis, Bone Morphogenetic Protein 2, Bone Morphogenetic Proteins, Cell Division, DNA-Binding Proteins, Hybridomas, Interleukin-2, MAP Kinase Kinase Kinases, Mice, Mitogen-Activated Protein Kinases, Recombinant Proteins, Signal Transduction, Smad6 Protein, Trans-Activators, Transfection, Transforming Growth Factor beta, p38 Mitogen-Activated Protein Kinases
Animals, Apoptosis, Bone Morphogenetic Protein 2, Bone Morphogenetic Proteins, Cell Division, DNA-Binding Proteins, Hybridomas, Interleukin-2, MAP Kinase Kinase Kinases, Mice, Mitogen-Activated Protein Kinases, Recombinant Proteins, Signal Transduction, Smad6 Protein, Trans-Activators, Transfection, Transforming Growth Factor beta, p38 Mitogen-Activated Protein Kinases
J. Biol. Chem.
Date: Jun. 09, 2000
PubMed ID: 10748100
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