Zu Ke, Hawthorn Lesleyann, Ip Clement
Department of Cancer Chemoprevention, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA.
Mol Cancer Ther. 2005 Jan;4(1):43-50.
Previously, alpha-tocopheryl succinate (alpha-TOS) has been reported to induce caspase-mediated apoptosis in PC-3 human prostate cancer cells. Caspase-9 was among several initiator caspases activated by alpha-TOS, suggesting a potential contribution of the intrinsic apoptotic pathway in mediating the response to alpha-TOS. Gene expression microarray was carried out as a screen to identify novel signaling molecules modulated by alpha-TOS, with a special focus on those known to play a role in mitochondria-mediated apoptosis. We discovered that Ask1, GADD45beta, and Sek1, three key components of the stress-activated mitogen-activated protein kinase pathway, are novel targets of alpha-TOS. Western blot analysis showed increased levels of phospho-Sek1 and phospho-c-Jun-NH2-kinase (JNK) in addition to total Ask1, GADD45beta, and Sek1. alpha-TOS also altered JNK-specific phosphorylation of Bcl-2 and Bim in a manner consistent with enhanced mitochondrial translocation of Bax and Bim. Because the expression level of most Bcl-2 family members remained unchanged, the posttranslational modification of Bcl-2 and Bim by JNK is likely to be a driving force in alpha-TOS activation of the intrinsic apoptotic pathway. Based on our findings, we propose a working model to capture the salient features of the apoptotic signaling circuitry of alpha-TOS.
此前，据报道琥珀酸α-生育酚（α-TOS）可诱导PC-3人前列腺癌细胞中半胱天冬酶介导的凋亡。半胱天冬酶-9是被α-TOS激活的几种起始半胱天冬酶之一，这表明内源性凋亡途径在介导对α-TOS的反应中可能发挥作用。进行基因表达微阵列筛选以鉴定受α-TOS调节的新型信号分子，特别关注那些已知在线粒体介导的凋亡中起作用的分子。我们发现应激激活的丝裂原活化蛋白激酶途径的三个关键成分Ask1、GADD45β和Sek1是α-TOS的新靶点。蛋白质印迹分析显示，除了Ask1、GADD45β和Sek1的总量外，磷酸化Sek1和磷酸化c-Jun氨基末端激酶（JNK）的水平也有所增加。α-TOS还以与Bax和Bim线粒体易位增强一致的方式改变了Bcl-2和Bim的JNK特异性磷酸化。由于大多数Bcl-2家族成员的表达水平保持不变，JNK对Bcl-2和Bim的翻译后修饰可能是α-TOS激活内源性凋亡途径的驱动力。基于我们的发现，我们提出了一个工作模型来描述α-TOS凋亡信号通路的显著特征。
