Transcriptional and Post-Transcriptional Regulation of Proangiogenic Factors by the Unfolded Protein Response
Transcriptional and Post-Transcriptional Regulation of Proangiogenic Factors by the Unfolded Protein Response
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DOI：
10.1371/journal.pone.0012521
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发表时间：
2010-09-02
期刊：
影响因子：
3.7
通讯作者：
Hendershot, Linda M.
中科院分区：
文献类型：
--
作者：
Pereira, Ethel R.;Liao, Nan;Hendershot, Linda M.
背景：细胞外环境的不足会对内质网的环境产生不利影响，并影响新生蛋白质的成熟。由此产生的未折叠蛋白质的积累激活信号转导途径，称为未折叠蛋白质的反应，这主要是为了保护细胞在应激过程中，并有助于恢复体内平衡的ER。主要结果：微阵列分析未折叠蛋白质的反应，在人髓母细胞瘤细胞系毒胡萝卜素处理显示，除了已知的目标，大量的促血管生成因子上调。RealTime PCR分析证实，这些因子中的四种，VEGFA，FGF 2，血管生成素和IL 8，在多种细胞系中被各种ER应激诱导剂转录上调。我们对VEGFA调控的研究表明，XBP-1（S），一种UPR诱导的转录因子，结合到VEGFA启动子上的两个区域，并且对XBP-1缺失的小鼠胚胎成纤维细胞的分析表明，它有助于VEGFA响应ER应激的表达。另一种UPR诱导型转录因子ATF 4也与VEGFA基因结合，尽管其对VEGFA转录的贡献似乎相当温和。我们还发现，VEGFA mRNA的稳定性增加响应UPR激活，通过激活AMP激酶，表明增加的mRNA水平发生在两个调节点。在保持与mRNA水平，我们发现，VEGFA蛋白的分泌水平高达或高于实现在响应于hypoxia.Conclusions和意义：我们的研究结果表明，UPR在诱导血管生成的积极调节发挥了重要作用。它还在转录、转录后和翻译后水平调节VEGFA表达，并且可能对响应于正常生理线索以及在病理条件如癌症中促进血管生成具有广泛意义。
Background: Inadequate extracellular conditions can adversely affect the environment of the ER and impinge on the maturation of nascent proteins. The resultant accumulation of unfolded proteins activates a signal transduction pathway, known as the unfolded protein response, which serves primarily to protect the cell during stress and helps restore homeostasis to the ER.Principal Findings: Microarray analysis of the unfolded protein response in a human medulloblastoma cell line treated with thapsigargin revealed that, in addition to known targets, a large number of proangiogenic factors were up-regulated. RealTime PCR analyses confirmed that four of these factors, VEGFA, FGF2, angiogenin and IL8, were transcriptionally upregulated in multiple cell lines by various ER stress inducers. Our studies on VEGFA regulation revealed that XBP-1(S), a UPRinducible transcription factor, bound to two regions on the VEGFA promoter, and analysis of XBP-1 null mouse embryonic fibroblasts revealed that it contributes to VEGFA expression in response to ER stress. ATF4, another UPR-inducible transcription factor, also binds to the VEGFA gene, although its contribution to VEGFA transcription appeared to be fairly modest. We also found that VEGFA mRNA stability is increased in response to UPR activation, via activation of AMP kinase, demonstrating that increased mRNA levels occur at two regulatory points. In keeping with the mRNA levels, we found that VEGFA protein is secreted at levels as high as or higher than that achieved in response to hypoxia.Conclusions and Significance: Our results indicate that the UPR plays a significant role in inducing positive regulators of angiogenesis. It also regulates VEGFA expression at transcriptional, post-transcriptional and post-translational levels and is likely to have widespread implications for promoting angiogenesis in response to normal physiological cues as well as in pathological conditions like cancer.