Livne A, Shtrichman R, Kleinberger T
The Gonda Center of Molecular Microbiology, The Bruce Rappaport Faculty of Medicine, Technion, Haifa 31096, Israel.
J Virol. 2001 Jan;75(2):789-98. doi: 10.1128/JVI.75.2.789-798.2001.
Adenovirus E4orf4 protein has been shown to induce transformed cell-specific, protein phosphatase 2A-dependent, and p53-independent apoptosis. It has been further reported that the E4orf4 apoptotic pathway is caspase-independent in CHO cells. Here, we show that E4orf4 induces caspase activation in the human cell lines H1299 and 293T. Caspase activation is required for apoptosis in 293T cells, but not in H1299 cells. Dominant negative mutants of caspase-8 and the death receptor adapter protein FADD/MORT1 inhibit E4orf4-induced apoptosis in 293T cells, suggesting that E4orf4 activates the death receptor pathway. Cytochrome c is released into the cytosol in E4orf4-expressing cells, but caspase-9 is not required for induction of apoptosis. Furthermore, E4orf4 induces accumulation of reactive oxygen species (ROS) in a caspase-8- and FADD/MORT1-dependent manner, and inhibition of ROS generation by 4,5-dihydroxy-1, 3-benzene-disulfonic acid (Tiron) inhibits E4orf4-induced apoptosis. Thus, our results demonstrate that E4orf4 engages the death receptor pathway to generate at least part of the molecular events required for E4orf4-induced apoptosis.
腺病毒E4orf4蛋白已被证明可诱导转化细胞特异性、蛋白磷酸酶2A依赖性和p53非依赖性凋亡。进一步报道称，E4orf4凋亡途径在CHO细胞中不依赖于半胱天冬酶。在此，我们表明E4orf4在人细胞系H1299和293T中诱导半胱天冬酶激活。半胱天冬酶激活在293T细胞的凋亡中是必需的，但在H1299细胞中不是。半胱天冬酶-8的显性负性突变体和死亡受体衔接蛋白FADD/MORT1抑制E4orf4诱导的293T细胞凋亡，表明E4orf4激活死亡受体途径。细胞色素c在表达E4orf4的细胞中释放到细胞质中，但凋亡诱导不需要半胱天冬酶-9。此外，E4orf4以半胱天冬酶-8和FADD/MORT1依赖性方式诱导活性氧（ROS）积累，4,5-二羟基-1,3-苯二磺酸（Tiron）抑制ROS生成可抑制E4orf4诱导的凋亡。因此，我们的结果表明，E4orf4参与死亡受体途径以产生E4orf4诱导凋亡所需的至少部分分子事件。
