RT Journal Article SR Electronic T1 Cell Stress Gives a Red Light to the Mitochondrial Cell Death Pathway JF Science Signaling JO Sci. Signal. FD American Association for the Advancement of Science SP pe9 OP pe9 DO 10.1126/stke.17pe9 VO 1 IS 7 A1 Guicciardi, M. Eugenia A1 Gores, Gregory J. YR 2008 UL http://stke.sciencemag.org/content/1/7/pe9.abstract AB Although the ultimate outcome of prolonged exposure of cells to stress is often death, the early response appears to be the activation of survival pathways that are likely to give the cell an opportunity to repair low-level damage. How these stress-initiated survival pathways influence B cell lymphoma/leukemia 2 (Bcl-2) proteins, the core cell death machinery, has remained unclear; however, two papers now provide insight into stress-mediated survival mechanisms. The liver is unusually resistant to p53-mediated apoptosis. It appears that p53-mediated induction of the gene that encodes insulin-like growth factor–binding protein-1 (IGFBP1) attenuates the cell death response in hepatocytes by preventing the formation of a complex between p53 and the proapoptotic protein BAK. This is especially interesting as IGFBP1 is not a member of the Bcl-2 family, yet it inhibited BAK. In three unrelated cell lines, another regulatory interaction that influences cell survival occurs at the mitochondria. In this case, protein phosphatase 1γ (PP1γ) regulated the phosphorylation status of the Bcl-2/Bcl-XL–associated death promoter (BAD). The prefoldin family member URI is normally phosphorylated by S6 kinase 1, which liberates PP1γ from a URI-PP1γ complex. However, the withdrawal of growth factors or nutrients stabilizes this complex, which renders PP1γ inactive. The net response of this stress stimulus is an increased abundance of phosphorylated BAD, which raises the threshold required to trigger cell death. These two studies have identified new players and mechanisms that integrate stress responses and cell death.