title: Constitutive and functional expression of YB-1 in microglial cells.
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.
authors.affiliation: Institute of Biochemistry and Cell Biology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Electronic address: gerburg.keilhoff@med.ovgu.de.
authors.forename: G
authors.initials: G
authors.lastname: Keilhoff
authors.affiliation: Institute of Biochemistry and Cell Biology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Electronic address: max.titze@st.ovgu.de.
authors.forename: M
authors.initials: M
authors.lastname: Titze
authors.affiliation: Department of Anesthesiology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Electronic address: torben.esser@med.ovgu.de.
authors.forename: T
authors.initials: T
authors.lastname: Esser
authors.affiliation: Institute of Biochemistry and Cell Biology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Electronic address: kristina.langnaese@med.ovgu.de.
authors.forename: K
authors.initials: K
authors.lastname: Langnaese
authors.affiliation: Department of Anesthesiology, Medical Faculty, University of Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Electronic address: uwe.ebmeyer@med.ovgu.de.
authors.forename: U
authors.initials: U
authors.lastname: Ebmeyer
mesh_terms: D000818:Animals; D001237:Asphyxia / Q000150:complications; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed; D004195:Disease Models, Animal; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000172:deficiency; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006323:Heart Arrest / Q000209:etiology / Q000473:pathology*; D019394:Ki-67 Antigen / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D051840:Y-Box-Binding Protein 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: C100745:Aif1 protein, rat; D002135:Calcium-Binding Proteins; D039561:Eukaryotic Initiation Factor-4E; D005904:Glial Fibrillary Acidic Protein; D019394:Ki-67 Antigen; D008070:Lipopolysaccharides; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D051840:Y-Box-Binding Protein 1; D049452:Green Fluorescent Proteins; D046988:Proteasome Endopeptidase Complex; D005947:Glucose; D010100:Oxygen
keywords: BV-2 cells; YB-1; hippocampus; microglia; neurodegeneration; rat cardiac arrest model