Keilhoff G, Titze M, Esser T, Langnaese K, Ebmeyer U
Institute of Biochemistry and Cell Biology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany.
Department of Anesthesiology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany.
Neuroscience. 2015 Aug 20;301:439-53. doi: 10.1016/j.neuroscience.2015.06.023. Epub 2015 Jun 20.
Y-box-binding protein (YB-1) is a member of the cold-shock protein family and participates in a wide variety of DNA/RNA-dependent cellular processes including DNA repair, transcription, mRNA splicing, packaging, and translation. At the cellular level, YB-1 is involved in cell proliferation and differentiation, stress responses, and malignant cell transformation. A general role for YB-1 during inflammation has also been well described; however, there are minimal data concerning YB-1 expression in microglia, which are the immune cells of the brain. Therefore, we studied the expression of YB-1 in a clinically relevant global ischemia model for neurological injury following cardiac arrest. This model is characterized by massive neurodegeneration of the hippocampal CA1 region and the subsequent long-lasting activation of microglia. In addition, we studied YB-1 expression in BV-2 cells, which are an accepted microglia culture model. BV-2 cells were stressed by oxygen/glucose deprivation (OGD), OGD-relevant mediators, lipopolysaccharide (LPS), and phagocytosis-inducing cell debris and nanoparticles. Using quantitative polymerase chain reaction (PCR), we show constitutive expression of YB-1 transcripts in unstressed BV-2 cells. The functional upregulation of the YB-1 protein was demonstrated in microglia in vivo and in BV-2 cells in vitro. All stressors except for LPS were potent enhancers of the level of YB-1 protein, which appears to be regulated primarily by proteasomal degradation and, to a lesser extent, by the activation (phosphorylation) of the translation initiation factor eIF4E. The proteasome of BV-2 cells is impaired by OGD, which results in decreased protein degradation and therefore increased levels of YB-1 protein. LPS induces proteasome activity, which enables the level of YB-1 protein to remain at control levels despite enhanced protein ubiquitination. The proteasome inhibitor MG-132 was able to increase YB-1 protein levels in control and LPS-treated cultures. YB-1 upregulation was not accompanied by its translocation from the cytoplasm to the nucleus. YB-1 induction appeared to be related to microglial proliferation because it was partially co-regulated with Ki67. In addition, YB-1 protein levels correlated with microglia phagocytic activity because its upregulation could also be induced by inert NPs.
Y盒结合蛋白（YB-1）是冷休克蛋白家族的成员，参与多种依赖DNA/RNA的细胞过程，包括DNA修复、转录、mRNA剪接、包装和翻译。在细胞水平上，YB-1参与细胞增殖和分化、应激反应以及恶性细胞转化。YB-1在炎症过程中的一般作用也有详细描述；然而，关于小胶质细胞（大脑的免疫细胞）中YB-1表达的数据极少。因此，我们研究了YB-1在心脏骤停后神经损伤的临床相关全脑缺血模型中的表达。该模型的特征是海马CA1区大量神经退行性变以及随后小胶质细胞的长期激活。此外，我们研究了BV-2细胞（一种公认的小胶质细胞培养模型）中YB-1的表达。BV-2细胞受到氧/葡萄糖剥夺（OGD）、与OGD相关的介质、脂多糖（LPS）以及诱导吞噬的细胞碎片和纳米颗粒的刺激。使用定量聚合酶链反应（PCR），我们显示在未受刺激的BV-2细胞中YB-1转录本的组成性表达。YB-1蛋白的功能性上调在体内小胶质细胞和体外BV-2细胞中得到证实。除LPS外，所有应激源都是YB-1蛋白水平的有效增强剂，其上调似乎主要受蛋白酶体降解调节，在较小程度上受翻译起始因子eIF4E的激活（磷酸化）调节。OGD会损害BV-2细胞的蛋白酶体，导致蛋白质降解减少，从而使YB-1蛋白水平升高。LPS诱导蛋白酶体活性，尽管蛋白质泛素化增强，但能使YB-1蛋白水平保持在对照水平。蛋白酶体抑制剂MG-132能够增加对照和LPS处理培养物中的YB-1蛋白水平。YB-1的上调并未伴随其从细胞质向细胞核的转位。YB-1的诱导似乎与小胶质细胞增殖有关，因为它与Ki67部分共同调节。此外，YB-1蛋白水平与小胶质细胞吞噬活性相关，因为其上调也可由惰性纳米颗粒诱导。
