Zha J, Harada H, Osipov K, Jockel J, Waksman G, Korsmeyer S J
Howard Hughes Medical Institute, Department of Medicine and Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Biol Chem. 1997 Sep 26;272(39):24101-4. doi: 10.1074/jbc.272.39.24101.
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.
BAD与抗凋亡分子BCL-2和BCL-XL相互作用并促进细胞凋亡。BAD会响应生存因子白细胞介素-3而在丝氨酸残基上发生磷酸化。磷酸化的BAD无法在膜位点与BCL-XL或BCL-2结合，而是存在于与14-3-3结合的胞质溶胶中。我们在此报告，缺失图谱分析和定点诱变确定了BAD内的一个BH3结构域，该结构域对于其与BCL-XL的异二聚化及其死亡激动剂活性均被证明是必需的。在BH3两亲性α-螺旋中将保守的Leu151替换为Ala会消除这两种功能。BAD Leu151突变体主要存在于与14-3-3结合的胞质溶胶中。BCL-2的BH3结构域对于BCL-2/BAD相互作用也很重要。这些结果确立了BAD内BH3结构域的关键作用，并提供了证据表明BAD可能作为一种死亡配体发挥作用，其促凋亡活性需要与BCL-XL异二聚化。
