MOE Key Laboratory of Laser Life Science and College of Biophotonics, South China Normal University, Guangzhou, China.
Department of Pain Management, The First Affiliated Hospital of Jinan University, Guangzhou, China.
Cell Mol Life Sci. 2020 Jun;77(12):2387-2406. doi: 10.1007/s00018-019-03286-z. Epub 2019 Sep 6.
The stoichiometry and affinity of Bcl-2 family complexes are essential information for understanding how their interactome network is orchestrated to regulate mitochondrial permeabilization and apoptosis. Based on over-expression model system, FRET analysis was used to quantify the protein-protein interactions among Bax, Bcl-xL, Bad and tBid in healthy and apoptotic cells. Our data indicate that the stoichiometry and affinity of Bcl-2 complexes are dependent on their membrane environment. Bcl-xL, Bad and tBid can form hetero-trimers in mitochondria. Bcl-xL binds preferentially to Bad, then to tBid and Bax in mitochondria, whilst Bcl-xL displays higher affinity to Bad or tBid than to itself. Strikingly, Bax can bind to Bcl-xL in cytosol. In cytosol of apoptotic cells, Bcl-xL associates with Bax to form hetero-trimer with 1:2 stoichiometry, while Bcl-xL associates with Bad to form hetero-trimer with 2:1 stoichiometry and Bcl-xL associates with tBid to form hetero-dimer. In mitochondria, Bcl-xL associates with Bax/Bad to form hetero-dimer in healthy cells, while Bcl-xL associates with Bad to form hetero-tetramer with 3:1 stoichiometry in apoptotic cells.
Bcl-2 家族复合物的化学计量和亲和力是理解其互作网络如何调控线粒体通透化和细胞凋亡的重要信息。基于过表达模型系统，我们使用 FRET 分析来定量研究 Bax、Bcl-xL、Bad 和 tBid 蛋白在健康和凋亡细胞中的蛋白-蛋白相互作用。我们的数据表明，Bcl-2 复合物的化学计量和亲和力取决于其膜环境。Bcl-xL、Bad 和 tBid 可以在线粒体中形成异源三聚体。Bcl-xL 在优先与 Bad 结合，然后与 tBid 和 Bax 结合，而 Bcl-xL 与 Bad 或 tBid 的亲和力高于自身。值得注意的是，Bax 可以在细胞质中与 Bcl-xL 结合。在凋亡细胞的细胞质中，Bcl-xL 与 Bax 形成具有 1:2 化学计量的异源三聚体，而 Bcl-xL 与 Bad 形成具有 2:1 化学计量的异源三聚体，与 tBid 形成异源二聚体。在线粒体中，Bcl-xL 在健康细胞中与 Bax/Bad 形成异源二聚体，而在凋亡细胞中与 Bad 形成具有 3:1 化学计量的异源四聚体。
