Soldatenkov V A, Dritschilo A
Department of Radiation Medicine, Georgetown University Medical Center, Washington, D.C. 20007, USA.
Cancer Res. 1997 Sep 15;57(18):3881-5.
Induction of apoptosis in Ewing's sarcoma cells by ionizing radiation is accompanied by accumulation of ubiquitinated proteins preferentially in the form of conjugates with M(r) greater than 75,000. Furthermore, enhanced antiubiquitin immunofluorescence was detected only in cells that underwent radiation-induced apoptosis, suggesting that the observed alterations in protein ubiquitination are specific to the apoptotic process. To determine the role of the proteasome in apoptosis-associated accumulation of ubiquitin-protein conjugates, we used lactacystin, a highly selective inhibitor of proteasome proteolytic activity. Exposure of Ewing's sarcoma cells to lactacystin resulted in accumulation of ubiquitinated proteins and activation of a Bcl-2-sensitive apoptotic pathways. The latter led to proteolytic cleavage of poly(ADP-ribose) polymerase and fragmentation of nuclear DNA. These findings suggest that proteasome function is required for apoptosis-specific accumulation of ubiquitinated proteins and indicate that functional disorder of the ubiquitin-proteasome system may play an important role in the apoptotic cell death pathway.
电离辐射诱导尤因肉瘤细胞凋亡的过程中，伴随着泛素化蛋白的积累，这些泛素化蛋白优先以分子量大于75,000的缀合物形式存在。此外，仅在经历辐射诱导凋亡的细胞中检测到增强的抗泛素免疫荧光，这表明观察到的蛋白质泛素化改变是凋亡过程所特有的。为了确定蛋白酶体在凋亡相关的泛素 - 蛋白缀合物积累中的作用，我们使用了乳胞素，一种蛋白酶体蛋白水解活性的高度选择性抑制剂。将尤因肉瘤细胞暴露于乳胞素会导致泛素化蛋白的积累以及Bcl - 2敏感凋亡途径的激活。后者导致聚（ADP - 核糖）聚合酶的蛋白水解切割和核DNA的片段化。这些发现表明蛋白酶体功能是泛素化蛋白凋亡特异性积累所必需的，并表明泛素 - 蛋白酶体系统的功能紊乱可能在凋亡细胞死亡途径中起重要作用。
