Li Qing, Ching Arthur Kar-Keung, Chan Ben Chung-Lap, Chow Stephanie Ka-Yee, Lim Pak-Leong, Ho Tony Cheong-Yip, Ip Wai-Ki, Wong Chun-Kwok, Lam Christopher Wai-Kei, Lee Kenneth Ka-Ho, Chan John Yeuk-Hon, Chui Yiu-Loon
Clinical Immunology Unit and Sir Y. K. Pao Centre for Cancer, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong Special Administrative Region, China.
J Biol Chem. 2004 Dec 10;279(50):52106-16. doi: 10.1074/jbc.M408678200. Epub 2004 Oct 1.
BRE, brain and reproductive organ-expressed protein, was found previously to bind the intracellular juxtamembrane domain of a ubiquitous death receptor, tumor necrosis factor receptor 1 (TNF-R1), and to down-regulate TNF-alpha-induced activation of NF-kappaB. Here we show that BRE also binds to another death receptor, Fas, and upon overexpression conferred resistance to apoptosis induced by TNF-alpha, anti-Fas agonist antibody, cycloheximide, and a variety of stress-related stimuli. However, down-regulation of the endogenous BRE by small interfering RNA increased apoptosis to TNF-alpha, but nottoetoposide, indicating that the physiological antiapoptotic role of this protein is specific to death receptor-mediated apoptosis. We further demonstrate that BRE mediates antiapoptosis by inhibiting the mitochondrial apoptotic machinery but without translocation to the mitochondria or nucleus or down-regulation of the cellular level of truncated Bid. Dissociation of BRE rapidly from TNF-R1, but not from Fas, upon receptor ligation suggests that this protein interacts with the death inducing signaling complex during apoptotic induction. Increased association of BREwith phosphorylated, sumoylated, and ubiquitinated proteins after death receptor stimulation was also detected. We conclude that in contrast to the truncated Bid that integrates mitochondrial apoptosis to death receptor-triggered apoptotic cascade, BRE inhibits the integration. We propose that BRE inhibits, by ubiquitination-like activity, components in or proximal to the death-inducing signaling complexes that are necessary for activation of the mitochondria.
BRE，即脑和生殖器官表达蛋白，先前被发现可结合一种普遍存在的死亡受体——肿瘤坏死因子受体1（TNF-R1）的细胞内近膜结构域，并下调肿瘤坏死因子-α（TNF-α）诱导的核因子κB（NF-κB）激活。在此我们表明，BRE还可结合另一种死亡受体Fas，过表达时可赋予细胞对TNF-α、抗Fas激动剂抗体、放线菌酮以及多种应激相关刺激诱导的凋亡的抗性。然而，通过小干扰RNA下调内源性BRE可增加细胞对TNF-α的凋亡，但对依托泊苷无此作用，这表明该蛋白的生理抗凋亡作用对死亡受体介导的凋亡具有特异性。我们进一步证明，BRE通过抑制线粒体凋亡机制介导抗凋亡作用，但不转位至线粒体或细胞核，也不会下调截短型Bid的细胞水平。受体连接后，BRE迅速从TNF-R1解离，但不从Fas解离，这表明该蛋白在凋亡诱导过程中与死亡诱导信号复合物相互作用。死亡受体刺激后，还检测到BRE与磷酸化、SUMO化和泛素化蛋白的结合增加。我们得出结论，与将线粒体凋亡整合到死亡受体触发的凋亡级联反应中的截短型Bid不同，BRE抑制这种整合。我们提出，BRE通过类泛素化活性抑制死亡诱导信号复合物中或其近端的、激活线粒体所必需的成分。
