Proteomic Analysis Of Nur77 Effect On Lipopolysaccharide-Induced Microglia Activation

[Objective]Microglia are critical players of immune response in central nervous system.Nur77 is highly expressed in the central nervous system and is involved in biological processes such as inflammation and cell proliferation.Our study aims to explore potential role of Nur77 on lipopolysaccharide(LPS)-induced microglial activation.[Methods]Primary wild type and Nur77-/-microglia were stimulated with LPS and protein extracts were detected by mass spectrometry.Q-PCR and western blotting were performed to validate candidate proteins.[Results]A total of 2004 proteins were identified,with 749 and 677 significant differently expressed proteins between wild type and Nur77-/-microglia in resting and activating microglia,respectively.Gene ontology analysis was performed to determine biological information of the differently expressed proteins in Nur77-/-microglia after LPS.Cellular components of up-regulated proteins are mainly related to ribosome,ribonucleoprotein complex,and cytosolic small ribosomal subunit.While down-regulated proteins are mainly located in proteasome complex,proteasome regulatory particle and proteasome accessory complex.According to molecular function,higher expressed proteins are involved in aminopeptidase activity,glycogen phosphorylase activity,and phosphorylase activity,while lower expressed proteins are related more close with nucleosomal DNA binding,syntaxin binding,SNAP receptor activity.Biological progresses of up-regulated proteins are mainly related to protein transport,intracellular protein transport,and vesicle-mediated transport and so on,while down-regulated proteins mainly involved in the process about vesicle docking,vesicle fusion,intracellular protein transport,and so on.Signaling pathway analysis showed that significant differentially expressed proteins in LPS-treated Nur77-/-microglia were distributed in important signaling pathways of microglia activation,including Toll-like receptor signaling pathway,MAPK signaling pathway,FcyR-mediated phagocytosis,and chemokine signaling pathways.Furthermore,we found that Nur77 could be the upstream protein of vavl and ERK1/2 signaling pathway.[Conclusions]In this study,we mainly studied the changes of protein expression in Nur77 knockout microglia and explored the effect of Nur77 on microglia activation after LPS.After LPS,Nur77 can affect the activation of microglia signaling pathway,including Toll-like receptor signaling pathway,MAPK signaling pathway,Fc?R-mediated phagocytosis and chemotaxis related signaling pathway.At the same time,we also found for the first time that Nur77 can regulate the activation of microglia induced by LPS through ERK1/2 signaling pathway and Vavl expression.The aim of this study was to provide a new perspective for studying the role of LPS in the activation of microglia induced by Nur77.