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. CONCLUSION: 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. GENERAL SIGNIFICANCE: 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.
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. CONCLUSION: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. GENERAL SIGNIFICANCE: 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.