Constitutive and functional expression of YB-1 in microglial cells. (20th August 2015)

• Record Type: Journal Article
• Authors: Keilhoff, G.; Titze, M.; Esser, T.; Langnaese, K.; Ebmeyer, U.
• Is Part Of: Neuroscience. Volume 301(2015)
• Page Start: 439
• Page End: 453
• Publication Date: 2015-08-20
• Subjects: ACA asphyxial cardiac arrest -- DAPI 4′, 6-diamidino-2-phenylindole -- DMEM Dulbecco's modified Eagle medium -- FCS fetal calf serum -- IPPV intermittent positive pressure ventilation -- LPS lipopolysaccharide -- MAP mean arterial pressure -- MNP magnetic nanoparticle -- ODG oxygen/glucose deprivation -- PBS phosphate-buffered saline -- PCR polymerase chain reaction -- ROSC return of spontaneous circulation -- YB-1 Y-box-binding protein; BV-2 cells -- hippocampus -- microglia -- neurodegeneration -- rat cardiac arrest model -- YB-1; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2015.06.023
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: YB-1 mRNA is constitutively expressed and functionally translated in microglia/BV-2 cells. YB-1 protein increases as a result of OGD, OGD-relevant mediators and phagocytosis-inducing factors. LPS is a less effective stimulus of YB-1 expression in BV-2 cells. YB-1 protein levels were primarily regulated by proteasomal degradation and less so by eIF4E activation (phosphorylation). YB-1 up-regulation was not accompanied by its translocation from the cytoplasm to the nucleus. Abstract: 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.