Department of Neuroscience for Drug Discovery, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
Biochem Biophys Res Commun. 2010 Mar 12;393(3):514-8. doi: 10.1016/j.bbrc.2010.02.038. Epub 2010 Feb 10.
Reduction in or dysfunction of glutamate transporter 1 (GLT1) is linked to several neuronal disorders such as stroke, Alzheimer's disease, and amyotrophic lateral sclerosis. However, the detailed mechanism underlying GLT1 regulation has not been fully elucidated. In the present study, we first demonstrated the effects of mammalian target of rapamycin (mTOR) signaling on GLT1 regulation. We prepared astrocytes cultured in astrocyte-defined medium (ADM), which contains several growth factors including epidermal growth factor (EGF) and insulin. The levels of phosphorylated Akt (Ser473) and mTOR (Ser2448) increased, and GLT1 levels were increased in ADM-cultured astrocytes. Treatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor or an Akt inhibitor suppressed the phosphorylation of Akt (Ser473) and mTOR (Ser2448) as well as decreased ADM-induced GLT1 upregulation. Treatment with the mTOR inhibitor rapamycin decreased GLT1 protein and mRNA levels. In contrast, rapamycin did not affect Akt (Ser473) phosphorylation. Our results suggest that mTOR is a downstream target of the PI3K/Akt pathway regulating GLT1 expression.
谷氨酸转运体 1（GLT1）的减少或功能障碍与几种神经元疾病有关，如中风、阿尔茨海默病和肌萎缩侧索硬化症。然而，GLT1 调节的详细机制尚未完全阐明。在本研究中，我们首先证明了哺乳动物雷帕霉素靶蛋白（mTOR）信号对 GLT1 调节的影响。我们制备了在星形胶质细胞定义培养基（ADM）中培养的星形胶质细胞，该培养基包含几种生长因子，包括表皮生长因子（EGF）和胰岛素。ADM 培养的星形胶质细胞中磷酸化 Akt（Ser473）和 mTOR（Ser2448）的水平升高，GLT1 水平升高。用磷脂酰肌醇 3-激酶（PI3K）抑制剂或 Akt 抑制剂处理可抑制 Akt（Ser473）和 mTOR（Ser2448）的磷酸化，并降低 ADM 诱导的 GLT1 上调。用 mTOR 抑制剂雷帕霉素处理可降低 GLT1 蛋白和 mRNA 水平。相比之下，雷帕霉素不影响 Akt（Ser473）的磷酸化。我们的结果表明，mTOR 是调节 GLT1 表达的 PI3K/Akt 通路的下游靶标。
