BAD contributes to RAF-mediated proliferation and cooperates with B-RAF-V600E in cancer signaling

Department of Microbiology, Biocenter, University of Würzburg, 97074 Würzburg, Germany.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2011; 286(20):17934-44. DOI: 10.1074/jbc.M110.177345
Source: PubMed


BAD (Bcl-2 antagonist of cell death) belongs to the proapoptotic BH3-only subfamily of Bcl-2 proteins. Physiological activity of BAD is highly controlled by phosphorylation. To further analyze the regulation of BAD function, we investigated the role of recently identified phosphorylation sites on BAD-mediated apoptosis. We found that in contrast to the N-terminal phosphorylation sites, the serines 124 and 134 act in an antiapoptotic manner because the replacement by alanine led to enhanced cell death. Our results further indicate that RAF kinases represent, besides PAK1, BAD serine 134 phosphorylating kinases. Importantly, in the presence of wild type BAD, co-expression of survival kinases, such as RAF and PAK1, leads to a strongly increased proliferation, whereas substitution of serine 134 by alanine abolishes this process. Furthermore, we identified BAD serine 134 to be strongly involved in survival signaling of B-RAF-V600E-containing tumor cells and found that phosphorylation of BAD at this residue is critical for efficient proliferation in these cells. Collectively, our findings provide new insights into the regulation of BAD function by phosphorylation and its role in cancer signaling.

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    • "Contradictive reports appeared that increased BAD expression stimulates proliferation of prostate cancer cells [28]. Knockdown of BAD also led to marked inhibition of proliferation in A375 and SK-MEL-28 malignant melanoma cells, and this growth inhibition could be abrogated by overexpression of wild type BAD [29]. Additionally, in our study, no differences of proliferation were observed in SK-MES-1 squamous cell lung cancer cell. "
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