Takada Eiko, Shimo Kuniaki, Hata Kikumi, Abiake Maira, Mukai Yasuo, Moriyama Masami, Heasley Lynn, Mizuguchi Junichiro
Department of Immunology and Intractable Disease Research Center, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, 160-8402, Tokyo, Japan.
Exp Cell Res. 2005 Apr 1;304(2):518-30. doi: 10.1016/j.yexcr.2004.11.015. Epub 2004 Dec 19.
Type I interferon (IFN)-induced antitumor action is due in part to apoptosis, but the molecular mechanisms underlying IFN-induced apoptosis remain largely unresolved. In the present study, we demonstrate that IFN-beta induced apoptosis and the loss of mitochondrial membrane potential (delta psi m) in the murine CH31 B lymphoma cell line, and this was accompanied by the up-regulation of CD95, but not CD95-ligand (CD95-L), tumor necrosis factor (TNF), or TNF-related apoptosis-inducing ligand (TRAIL). Pretreatment with anti-CD95-L mAb partially prevented the IFN-beta-induced loss of delta psi m, suggesting that the interaction of IFN-beta-up-regulated CD95 with CD95-L plays a crucial role in the induction of fratricide. IFN-beta induced a sustained activation of c-Jun NH2-terminal kinase 1 (JNK1), but not extracellular signal-regulated kinases (ERKs). The IFN-beta-induced apoptosis and loss of delta psi m were substantially compromised in cells overexpressing a dominant-negative form of JNK1 (dnJNK1), and it was slightly enhanced in cells carrying a constitutively active JNK construct, MKK7-JNK1 fusion protein. The IFN-beta-induced up-regulation of CD95 together with caspase-8 activation was also abrogated in the dnJNK1 cells while it was further enhanced in the MKK7-JNK1 cells. The levels of cellular FLIP (c-FLIP), competitively interacting with caspase-8, were down-regulated by stimulation with IFN-beta but were reversed by the proteasome inhibitor lactacystin. Collectively, the IFN-beta-induced sustained activation of JNK mediates apoptosis, at least in part, through up-regulation of CD95 protein in combination with down-regulation of c-FLIP protein.
I型干扰素（IFN）诱导的抗肿瘤作用部分归因于细胞凋亡，但其诱导细胞凋亡的分子机制仍未完全阐明。在本研究中，我们证明IFN-β可诱导小鼠CH31 B淋巴瘤细胞系发生凋亡并导致线粒体膜电位（Δψm）丧失，同时伴有CD95上调，但CD95配体（CD95-L）、肿瘤坏死因子（TNF）或TNF相关凋亡诱导配体（TRAIL）未上调。用抗CD95-L单克隆抗体预处理可部分阻止IFN-β诱导的Δψm丧失，这表明IFN-β上调的CD95与CD95-L之间的相互作用在诱导自相残杀中起关键作用。IFN-β可诱导c-Jun氨基末端激酶1（JNK1）持续激活，但不诱导细胞外信号调节激酶（ERK）激活。在过表达显性负性形式JNK1（dnJNK1）的细胞中，IFN-β诱导的细胞凋亡和Δψm丧失显著受损，而在携带组成型活性JNK构建体MKK7-JNK1融合蛋白的细胞中则略有增强。在dnJNK1细胞中，IFN-β诱导的CD95上调以及半胱天冬酶-8激活也被消除，而在MKK7-JNK1细胞中则进一步增强。细胞FLIP（c-FLIP）水平可与半胱天冬酶-8竞争性相互作用，经IFN-β刺激后下调，但蛋白酶体抑制剂乳胞素可使其逆转。总之，IFN-β诱导的JNK持续激活至少部分通过上调CD95蛋白并下调c-FLIP蛋白介导细胞凋亡。
