The regulatory protein GADD34 inhibits TRAIL-induced apoptosis via TRAF6/ERK-dependent stabilization of myeloid cell leukemia 1 in liver cancer cells
The regulatory protein GADD34 inhibits TRAIL-induced apoptosis via TRAF6/ERK-dependent stabilization of myeloid cell leukemia 1 in liver cancer cells
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调节蛋白 GADD34 通过 TRAF6/ERK 依赖性稳定肝癌细胞中的骨髓细胞白血病 1 来抑制 TRAIL 诱导的细胞凋亡
DOI：
10.1074/jbc.ra118.006029
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发表时间：
2019-04-12
影响因子：
4.8
通讯作者：
Jiang, Yangfu
中科院分区：
文献类型：
--
作者：
Song, Peiying;Yang, Songpeng;Jiang, Yangfu
GADD 34（growth arrest and DNA damage-inducible gene 34）在细胞对DNA损伤和内质网应激的反应中起着关键作用。GADD 34对不同刺激诱导的细胞凋亡事件具有相反的作用，但其原因尚不清楚。在这里，使用免疫印迹分析和各种分子遗传学方法在HepG 2和SMMC-7721细胞，我们证明，GADD 34保护肝细胞癌（HCC）细胞从肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导的凋亡稳定BCL-2家族成员，髓细胞白血病1（MCL-1）。我们发现GADD 34敲低降低了HCC细胞中MCL-1的水平，而GADD 34过表达上调了HCC细胞中MCL-1的表达。GADD 34不影响MCL-1的转录，但增强了MCL-1蛋白的稳定性。蛋白酶体抑制剂MG 132消除GADD 34耗竭诱导的MCL-1下调，表明GADD 34抑制MCL-1的蛋白酶体降解。此外，GADD 34过表达通过由E3泛素连接酶肿瘤坏死因子受体相关因子6（TRAF 6）和转化生长因子激活激酶1（MAP 3 K7）结合蛋白1（TAB 1）组成的信号传导轴促进细胞外信号调节激酶（ERK）磷酸化，后者介导GADD 34上调MCL-1。值得注意的是，TRAIL上调GADD 34和MCL-1水平，GADD 34和TRAF 6的敲低抑制了TRAIL对MCL-1的诱导。相应地，GADD 34敲低增强了TRAIL诱导的细胞凋亡，并且MCL-1过表达拯救了TRAIL处理的和GADD 34耗尽的HCC细胞免于细胞死亡。综上所述，这些发现表明GADD 34通过TRAF 6和ERK介导的MCL-1稳定抑制TRAIL诱导的HCC细胞凋亡。
GADD34 (growth arrest and DNA damage-inducible gene 34) plays a critical role in responses to DNA damage and endoplasmic reticulum stress. GADD34 has opposing effects on different stimuli-induced cell apoptosis events, but the reason for this is unclear. Here, using immunoblotting analyses and various molecular genetic approaches in HepG2 and SMMC-7721 cells, we demonstrate that GADD34 protects hepatocellular carcinoma (HCC) cells from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by stabilizing a BCL-2 family member, myeloid cell leukemia 1 (MCL-1). We found that GADD34 knockdown decreased MCL-1 levels and that GADD34 overexpression up-regulated MCL-1 expression in HCC cells. GADD34 did not affect MCL-1 transcription but enhanced MCL-1 protein stability. The proteasome inhibitor MG132 abrogated GADD34 depletion-induced MCL-1 down-regulation, suggesting that GADD34 inhibits the proteasomal degradation of MCL-1. Furthermore, GADD34 overexpression promoted extracellular signal-regulated kinase (ERK) phosphorylation through a signaling axis that consists of the E3 ubiquitin ligase tumor necrosis factor receptor-associated factor 6 (TRAF6) and transforming growth factor--activated kinase 1 (MAP3K7)-binding protein 1 (TAB1), which mediated the up-regulation of MCL-1 by GADD34. Of note, TRAIL up-regulated both GADD34 and MCL-1 levels, and knockdown of GADD34 and TRAF6 suppressed the induction of MCL-1 by TRAIL. Correspondingly, GADD34 knockdown potentiated TRAIL-induced apoptosis, and MCL-1 overexpression rescued TRAIL-treated and GADD34-depleted HCC cells from cell death. Taken together, these findings suggest that GADD34 inhibits TRAIL-induced HCC cell apoptosis through TRAF6- and ERK-mediated stabilization of MCL-1.