Wang K, Yin X M, Chao D T, Milliman C L, Korsmeyer S J
Department of Medicine and Pathology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Genes Dev. 1996 Nov 15;10(22):2859-69. doi: 10.1101/gad.10.22.2859.
The BCL-2 family of proteins consists of both antagonists (e.g., BCL-2) and agonists (e.g., BAX) that regulate apoptosis and compete through dimerization. The BH1 and BH2 domains of BCL-2 are required to heterodimerize with BAX and to repress cell death; conversely, the BH3 domain of BAX is required to heterodimerize with BCL-2 and to promote cell death. To extend this pathway, we used interactive cloning to identify Bid, which encodes a novel death agonist that heterodimerizes with either agonists (BAX) or antagonists (BCL-2). BID possesses only the BH3 domain, lacks a carboxy-terminal signal-anchor segment, and is found in both cytosolic and membrane locations. BID counters the protective effect of BCL-2. Moreover, expression of BID, without another death stimulus, induces ICE-like proteases and apoptosis. Mutagenesis revealed that an intact BH3 domain of BID was required to bind the BH1 domain of either BCL-2 or BAX. A BH3 mutant of BID that still heterodimerized with BCL-2 failed to promote apoptosis, dissociating these activities. In contrast, the only BID BH3 mutant that retained death promoting activity interacted with BAX, but not BCL-2. This BH3-only molecule supports BH3 as a death domain and favors a model in which BID represents a death ligand for the membrane-bound receptor BAX.
BCL-2蛋白家族由调节细胞凋亡的拮抗剂（如BCL-2）和激动剂（如BAX）组成，它们通过二聚化相互竞争。BCL-2的BH1和BH2结构域对于与BAX形成异源二聚体以及抑制细胞死亡是必需的；相反，BAX的BH3结构域对于与BCL-2形成异源二聚体以及促进细胞死亡是必需的。为了扩展这条通路，我们利用交互克隆技术鉴定出了Bid，它编码一种新型死亡激动剂，可与激动剂（BAX）或拮抗剂（BCL-2）形成异源二聚体。BID仅具有BH3结构域，缺乏羧基末端信号锚定片段，存在于细胞质和细胞膜中。BID可对抗BCL-2的保护作用。此外，在没有其他死亡刺激的情况下，BID的表达可诱导ICE样蛋白酶并引发细胞凋亡。诱变实验表明，BID完整的BH3结构域对于与BCL-2或BAX的BH1结构域结合是必需 的。一个仍能与BCL-2形成异源二聚体的BID BH3突变体无法促进细胞凋亡，从而将这些活性分离开来。相反，唯一保留死亡促进活性的BID BH3突变体与BAX相互作用，但不与BCL-2相互作用。这个仅含BH3的分子支持将BH3作为死亡结构域，并支持一种模型，即BID代表膜结合受体BAX的死亡配体。
