Lee J-J, Lee J-S, Cui M N, Yun H H, Kim H Y, Lee S H, Lee J-H
1] Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul, Korea [2] Catholic Cancer Research Institute, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Department of Biomedical Sciences, College of Medicine, Inha University, Incheon, Korea.
Cell Death Dis. 2014 Nov 20;5(11):e1537. doi: 10.1038/cddis.2014.501.
Cellular senescence is an important mechanism for preventing tumor progression. The elevated expression of Bcl-2-interacting cell death suppressor (BIS), an anti-apoptotic and anti-stress protein, often correlates with poor prognosis in several cancers including glioblastoma; however, the role of BIS in the regulation of senescence has not been well defined. Here, we describe for the first time that the depletion of BIS induces G1 arrest and cellular senescence through the accumulation of p27 that is independent of p53, p21 or p16. The increase in p27 expression in BIS-depleted cells was attributable to an impairment of the ubiquitin-mediated degradation of p27, which was caused by a decrease in S-phase kinase-associated protein 2 (SKP2) at the transcriptional level. As an underlying molecular mechanism, we demonstrate that the loss of activity of signal transducer and activator of transcription 3 (STAT3) was specifically linked to the suppression of SKP2 expression. Despite a reduction in phospho-STAT3 levels, total STAT3 levels were unexpectedly increased by BIS depletion, specifically in the insoluble fraction. Our results show that 14-3-3ζ expression is decreased by BIS knockdown and that 14-3-3ζ depletion per se significantly induced senescence phenotypes. In addition, the ectopic expression of 14-3-3ζ blocked senescence caused by BIS depletion, which was paralleled with a decrease in insoluble STAT3 in A172 glioblastoma cells. These findings indicate that the impairment of the protein quality control conferred by BIS and/or 14-3-3ζ is critical for BIS depletion-induced senescence. Moreover, BIS knockdown also induced senescence along with an accumulation of total STAT3 and p27 in several different cell types as well as embryonic fibroblasts derived from Bis-knock out mice with/without variations in 14-3-3ζ levels. Therefore, our findings suggest that a downregulation of BIS expression could serve as a potential strategy for restricting tumor progression via an induction of senescence through the regulation of STAT3/SKP2/p27 pathway.
细胞衰老 是预防肿瘤进展的重要机制。抗凋亡和抗应激蛋白Bcl-2相互作用细胞死亡抑制因子(BIS)的表达升高,在包括胶质母细胞瘤在内的几种癌症中,往往与预后不良相关;然而,BIS在衰老调节中的作用尚未明确界定。在此,我们首次描述,BIS的缺失通过p27的积累诱导G1期阻滞和细胞衰老,这一过程独立于p53、p21或p16。BIS缺失细胞中p27表达的增加归因于泛素介导的p27降解受损,这是由转录水平上S期激酶相关蛋白2(SKP2)的减少引起的。作为潜在的分子机制,我们证明信号转导和转录激活因子3(STAT3)活性的丧失与SKP2表达的抑制特异性相关。尽管磷酸化STAT3水平降低,但BIS缺失意外地增加了总STAT3水平,特别是在不溶性部分。我们的结果表明,BIS敲低会降低14-3-3ζ的表达,而14-3-3ζ的缺失本身会显著诱导衰老表型。此外,14-3-3ζ的异位表达阻止了由BIS缺失引起的衰老,这与A172胶质母细胞瘤细胞中不溶性STAT3的减少平行。这些发现表明,BIS和/或14-3-3ζ赋予的蛋白质质量控制受损对于BIS缺失诱导的衰老至关重要。此外,BIS敲低还在几种不同的细胞类型以及来自Bis基因敲除小鼠的胚胎成纤维细胞中诱导衰老,无论14-3-3ζ水平有无变化,都会伴随总STAT3和p27的积累。因此,我们的研究结果表明,下调BIS表达可能是一种潜在策略,通过调节STAT3/SKP2/p27途径诱导衰老来限制肿瘤进展。