Cuddeback S M, Yamaguchi H, Komatsu K, Miyashita T, Yamada M, Wu C, Singh S, Wang H G
Drug Discovery Program, H. Lee Moffitt Cancer Center and Research Institute, Department of Pharmacology and Therapeutics, University of South Florida, Tampa, Florida 33612, USA.
J Biol Chem. 2001 Jun 8;276(23):20559-65. doi: 10.1074/jbc.M101527200. Epub 2001 Mar 20.
Bax is a proapoptotic member of the Bcl-2 protein family that commits the cell to undergo programmed cell death in response to apoptotic stimuli. To gain further insights into Bax mechanisms, we have identified a novel Bax-binding protein, termed Bif-1, by using a yeast two-hybrid cloning technique. Bif-1 is an evolutionarily conserved cytoplasmic protein that contains a predicted Src homology 3 (SH3) domain located near its C terminus but shares no significant homology with members of the Bcl-2 family. A Northern blot analysis indicates that Bif-1 is expressed in most tissues with abundant expression in heart and skeletal muscle. Bif-1 is capable of interacting with Bax as demonstrated by yeast two-hybrid, coimmunoprecipitation, and immunofluorescence studies. Induction of apoptosis in murine pre-B hematopoietic cells FL5.12 by interleukin-3 withdrawal results in increased association of Bax with Bif-1, which is accompanied by a conformational change in the Bax protein. Overexpression of Bif-1 promotes Bax conformational change, caspase activation, and apoptotic cell death in FL5.12 cells following interleukin-3 deprivation. Bif-1 thus represents a new type of regulator of Bax-mediated signaling pathways for apoptosis.
Bax是Bcl-2蛋白家族的促凋亡成员，可使细胞在凋亡刺激下发生程序性细胞死亡。为了进一步深入了解Bax的作用机制，我们利用酵母双杂交克隆技术鉴定出一种新的Bax结合蛋白，命名为Bif-1。Bif-1是一种进化上保守的细胞质蛋白，在其C末端附近含有一个预测的Src同源3（SH3）结构域，但与Bcl-2家族成员没有显著同源性。Northern印迹分析表明，Bif-1在大多数组织中表达，在心脏和骨骼肌中表达丰富。酵母双杂交、免疫共沉淀和免疫荧光研究表明，Bif-1能够与Bax相互作用。白细胞介素-3撤除诱导小鼠前B造血细胞FL5.12凋亡，导致Bax与Bif-1的结合增加，同时Bax蛋白发生构象变化。在白细胞介素-3剥夺后，Bif-1的过表达促进FL5.12细胞中Bax的构象变化、半胱天冬酶激活和凋亡细胞死亡。因此，Bif-1代表了一种新型的Bax介导的凋亡信号通路调节因子。
