BH3 domain of BAD is required for heterodimerization with BCL-XL and pro-apoptotic activity.
BAD interacts with anti-apoptotic molecules BCL-2 and BCL-XL and promotes apoptosis. BAD is phosphorylated on serine residues in response to a survival factor, interleukin-3. Phosphorylated BAD cannot bind to BCL-XL or BCL-2 at membrane sites and is found in the cytosol bound to 14-3-3. We report here that deletion mapping and site-directed mutagenesis identified a BH3 domain within BAD that proved necessary for both its heterodimerization with BCL-XL and its death agonist activity. Substitution of the conserved Leu151 with Ala in the BH3 amphipathic alpha-helix abrogated both functions. The BAD Leu151 mutant was predominantly in the cytosol bound to 14-3-3. The BH3 domain of BCL-2 also proved important for BCL-2/BAD interaction. These results establish a critical role for a BH3 domain within BAD and provide evidence that BAD may function as a death ligand whose pro-apoptotic activity requires heterodimerization with BCL-XL.
Zha
J
J
Howard Hughes Medical Institute, Department of Medicine and Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Harada
H
H
Osipov
K
K
Jockel
J
J
Waksman
G
G
Korsmeyer
S J
SJ
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019281:Dimerization; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
C494820:Bad protein, mouse; C494812:Bcl2l1 protein, mouse; D002352:Carrier Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein