Abstract：
Glucose transporter-2 (GLUT2), a unique high capacity/low affinity, highly efficient membrane transporter and sensor, regulates hypothalamic astrocyte glucose phosphorylation and glycogen metabolism. The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway participates in glucose homeostasis, but its sensitivity to glucose-sensory cues is unknown. Current research used a hypothalamic astrocyte primary culture model to investigate whether glucoprivation causes PI3K/Akt/mTOR pathway activation in one or both sexes by GLUT2-dependent mechanisms. Glucoprivation did not alter astrocyte PI3K levels, yet up-regulated both phosphorylated derivatives in female and down-regulated male p60 phosphoprotein expression. GLUT2 siRNA pretreatment diminished glucoprivic patterns of PI3K and phospho-PI3K expression in each sex. Astrocyte Akt and phospho-Akt/Thr308 proteins exhibited divergent, sex-contingent responses to GLUT2 gene knockdown or glucoprivation. GLUT2 siRNA pretreatment exacerbated glucoprivic-associated Akt diminution in the female, and either amplified (male) or reversed (female) glucoprivic regulation of phospho-Akt/Thr308 expression. GLUT2 gene silencing down- (male) or up-(female) regulated mTOR protein, and phospho-mTOR protein in male. Male astrocyte mTOR and phospho-mTOR profile were refractory to glucoprivation, but glucose-deprived females showed GLUT2-independent mTOR inhibition and GLUT2-dependent phospho-mTOR up-augmentation. Results identify a larger number of glucoprivic-sensitive PI3K/Akt/mTOR pathway proteins in female versus male astrocytes, and document divergent responses of common glucose-sensitive targets. GLUT2 stimulates phosphoPI3K protein expression in each sex, but imposes differential control of PI3K, Akt, phospho-Akt/Thr308, mTOR, and phospho-mTOR profiles in male versus female. Data implicate GLUT2 as a driver of distinctive pathway protein responses to glucoprivation in female, but not male.
摘要：
葡萄糖转运蛋白-2（GLUT2），独特的高容量/低亲和力，高效的膜转运器和传感器，调节下丘脑星形胶质细胞葡萄糖磷酸化和糖原代谢。磷脂酰肌醇-3-激酶(PI3K)/蛋白激酶B(Akt)/哺乳动物雷帕霉素靶蛋白(mTOR)信号通路参与葡萄糖稳态,但它对葡萄糖感觉信号的敏感性是未知的。当前的研究使用下丘脑星形胶质细胞原代培养模型来研究葡萄糖化是否通过GLUT2依赖性机制导致一种或两种性别的PI3K/Akt/mTOR通路激活。葡萄糖调节没有改变星形胶质细胞PI3K水平，然而上调女性磷酸化衍生物和下调男性p60磷蛋白表达。GLUT2siRNA预处理减少了每种性别中PI3K和磷酸-PI3K表达的葡萄糖模式。星形胶质细胞Akt和磷酸-Akt/Thr308蛋白表现出不同的，性别对GLUT2基因敲低或葡萄糖分裂的反应。GLUT2siRNA预处理加剧了女性中与胰高血糖素相关的Akt减少，以及扩增的(雄性)或逆转的(雌性)磷酸-Akt/Thr308表达的葡糖嘌呤调节。GLUT2基因沉默下调（男性）或上调（女性）调节的mTOR蛋白，和磷酸化mTOR蛋白在男性。男性星形胶质细胞mTOR和磷酸-mTOR谱对葡萄糖生成是难治性的，但缺乏葡萄糖的女性显示GLUT2非依赖性mTOR抑制和GLUT2依赖性磷酸化mTOR升高.结果在女性星形胶质细胞和男性星形胶质细胞中鉴定出更多的对葡萄糖酸敏感的PI3K/Akt/mTOR通路蛋白。并记录常见葡萄糖敏感靶标的不同反应。GLUT2刺激每个性别的磷酸PI3K蛋白表达，但对PI3K进行差动控制，Akt,phospho-Akt/Thr308,mTOR,和磷酸化mTOR在男性和女性中的分布。数据暗示GLUT2是女性对葡萄糖化的独特途径蛋白反应的驱动因素，但不是男性。
