title: Mechanism of YB-1-mediated translational induction of GluR2 mRNA in response to neural activity through nAChR.
abstract: BACKGROUND
  We have reported previously that YB-1 induces translation of GluR2 mRNA in response to neural activity, and that HSP60 affects the association of YB-1 with polysomes. Here we examined the mechanism of YB-1-mediated translational activation of GluR2 mRNA through the nAChR.
  
  
  METHODS
  Expression of nAChRs in NG108-15 cells was verified. Translation of GluR2 mRNA and YB-1/HSP60 interaction were examined in nicotine-treated NG108-15 cells. Effects of inhibition of α7-nAChR and the PI3K/Akt pathway were investigated. The ratios of YB-1 to GluR2 mRNA and to HSP60 were explored in polysomal and non-polysomal fractions, respectively, and the role of HSP60 in cytoplasmic retention of YB-1 was evaluated.
  
  
  RESULTS
  Nicotine treatment transiently induced translation of GluR2 mRNA and Akt phosphorylation with a concomitant increase of YB-1/HSP60 interaction. Both α-bungarotoxin and LY294002 abolished the effects of nicotine. On a sucrose gradient, nicotine treatment shifted the distribution of YB-1 to much heavier-sedimenting polysome fractions. In these fractions, the ratio of YB-1 to its binding GluR2 mRNA was decreased, and ribosome association with the YB-1-bound GluR2 mRNA was increased. HSP60 was distributed only in the non-polysomal fractions as its binding to YB-1 increased. In HSP60-depleted cells, nicotine treatment induced nuclear localization of YB-1.
  
  
  CONCLUSIONS
  YB-1 is released from GluR2 mRNA during α7-nAChR-mediated neurotransmission, causing the PI3K/Akt pathway to recruit ribosomes into the translational machinery, and HSP60 is involved in cytoplasmic retention of polysome-free YB-1.
  
  
  CONCLUSIONS
  Activation of the PI3K/Akt pathway through the α7-nAChR and YB-1/HSP60 interaction are important for YB-1-mediated translational activation of GluR2 mRNA.
authors.affiliation: Department of Biochemistry, School of Pharmacy, Nihon University, Chiba, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Tanaka
authors.forename: Sachiyo
authors.initials: S
authors.lastname: Ohashi
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Moue
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002038:Bungarotoxins / Q000494:pharmacology; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005910:Glioma / Q000235:genetics / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D051379:Mice; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D009538:Nicotine / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011132:Polyribosomes; D014176:Protein Biosynthesis / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000378:metabolism; D009435:Synaptic Transmission; D014407:Tumor Cells, Cultured; D051840:Y-Box-Binding Protein 1 / Q000235:genetics / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: D002038:Bungarotoxins; D018834:Chaperonin 60; C579166:Chrna7 protein, mouse; C579165:Chrna7 protein, rat; D012333:RNA, Messenger; D018091:Receptors, AMPA; D011978:Receptors, Nicotinic; D051840:Y-Box-Binding Protein 1; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C104722:glutamate receptor ionotropic, AMPA 2