TY - JOUR
T1 - Survival-factor-induced phosphorylation of bad results in its dissociation from Bcl-xL but not Bcl-2
AU - Hirai, I.
AU - Wang, H. G.
PY - 2001/10/15
Y1 - 2001/10/15
N2 - The pro-apoptotic Bcl-2-family protein Bad heterodimerizes with Bcl-2 and Bcl-xL in the outer mitochondrial membranes, nullifying their anti-apoptotic activities and promoting cell death. We report that interleukin-3 (IL-3) stimulation induces Bad phosphorylation and triggers its translocation from mitochondria to cytoplasm in cells expressing Bcl-xL but not Bcl-2. Overexpression of Bad sensitized Bcl-xL-expressing FL5.12 cells to apoptosis induced by IL-3 deprivation, but had no effect on the viability of cells expressing Bcl-2. IL-3 stimulation induced Bad phosphorylation at Ser-112, impairing its binding to Bcl-xL and resulting in its association with 14-3-3 proteins in the cytosol. However, Ser-112 phosphorylation could not trigger Bad dissociation from mitochondria in FL5.12 cells expressing Bcl-2. In 293T cells expressing Bcl-XL, Bad was phosphorylated at three serines, 112, 136 and 155, and was largely localized in the cytosolic fraction. In contrast, overexpression of Bcl-2 prevented phosphorylation of Bad at Ser-136 and Ser-155, sequestering this protein in the mitochondrial membranes. When the N-terminal regions of Bcl-2 and Bcl-xL were swapped with each other, the Bcl-xL(N) Bcl-2 chimaeric protein (containing the N-terminal region of Bcl-XL) failed to prevent Bad phosphorylation in cells and was unable to block the cytosolic distribution of this proapoptotic protein. Additional experiments with the Bcl-2(N)-Bcl-xL chimaeric protein (containing the N-terminal region of Bcl-2) indicated that, although the N-terminal region of Bcl-2 is necessary, it is not sufficient for sequestering Bad in the mitochondrial membranes. These observations suggest that growth-factor-mediated phosphorylation of Bad contributes to the cytoprotective function of Bcl-xL but not Bcl-2.
AB - The pro-apoptotic Bcl-2-family protein Bad heterodimerizes with Bcl-2 and Bcl-xL in the outer mitochondrial membranes, nullifying their anti-apoptotic activities and promoting cell death. We report that interleukin-3 (IL-3) stimulation induces Bad phosphorylation and triggers its translocation from mitochondria to cytoplasm in cells expressing Bcl-xL but not Bcl-2. Overexpression of Bad sensitized Bcl-xL-expressing FL5.12 cells to apoptosis induced by IL-3 deprivation, but had no effect on the viability of cells expressing Bcl-2. IL-3 stimulation induced Bad phosphorylation at Ser-112, impairing its binding to Bcl-xL and resulting in its association with 14-3-3 proteins in the cytosol. However, Ser-112 phosphorylation could not trigger Bad dissociation from mitochondria in FL5.12 cells expressing Bcl-2. In 293T cells expressing Bcl-XL, Bad was phosphorylated at three serines, 112, 136 and 155, and was largely localized in the cytosolic fraction. In contrast, overexpression of Bcl-2 prevented phosphorylation of Bad at Ser-136 and Ser-155, sequestering this protein in the mitochondrial membranes. When the N-terminal regions of Bcl-2 and Bcl-xL were swapped with each other, the Bcl-xL(N) Bcl-2 chimaeric protein (containing the N-terminal region of Bcl-XL) failed to prevent Bad phosphorylation in cells and was unable to block the cytosolic distribution of this proapoptotic protein. Additional experiments with the Bcl-2(N)-Bcl-xL chimaeric protein (containing the N-terminal region of Bcl-2) indicated that, although the N-terminal region of Bcl-2 is necessary, it is not sufficient for sequestering Bad in the mitochondrial membranes. These observations suggest that growth-factor-mediated phosphorylation of Bad contributes to the cytoprotective function of Bcl-xL but not Bcl-2.
UR - http://www.scopus.com/inward/record.url?scp=0035886878&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035886878&partnerID=8YFLogxK
U2 - 10.1042/0264-6021:3590345
DO - 10.1042/0264-6021:3590345
M3 - Article
C2 - 11583580
AN - SCOPUS:0035886878
SN - 0264-6021
VL - 359
SP - 345
EP - 352
JO - Biochemical Journal
JF - Biochemical Journal
IS - 2
ER -