Roos M D, Han I O, Paterson A J, Kudlow J E
Division of Endocrinology and Metabolism, University of Alabama at Birmingham 35294, USA.
Am J Physiol. 1996 Mar;270(3 Pt 1):C803-11. doi: 10.1152/ajpcell.1996.270.3.C803.
Transforming growth factor-alpha (TGF-alpha) gene transcription is regulated by both epidermal growth factor (EGF) and glucose. Previous studies have suggested that the metabolism of glucose to glucosamine through the enzyme L-glutamine: D-fructose-6-phosphate amidotransferase (GFAT) plays a critical role in the glucose signaling. In this paper, we compared the role of GFAT in the glucose and EGF signals. We found that, although EGF stimulates GFAT mRNA accumulation in MDA-MB-468 cells, this effect of EGF occurred several hours after TGF-alpha transcription increased. MDA-MB-468 cells also exhibited a TGF-alpha transcriptional response to low concentrations of glucose. The TGF-alpha response to glucose but not EGF could be inhibited by a blocker of GFAT activity. Blockade of GFAT was confirmed by using Western blotting with the RL2 antibody, which recognizes an epitope on proteins containing N-acetylglucosamine. Exposure of cells to glucose increased the RL2 signal on several polypeptides, but this change could be blocked by inhibition of GFAT. These results support the notion that glucose stimulation of TGF-alpha expression requires GFAT, but EGF stimulation does not.
转化生长因子α（TGF-α）基因转录受表皮生长因子（EGF）和葡萄糖的调控。先前的研究表明，葡萄糖通过L-谷氨酰胺：D-果糖-6-磷酸酰胺转移酶（GFAT）代谢为葡糖胺在葡萄糖信号传导中起关键作用。在本文中，我们比较了GFAT在葡萄糖和EGF信号中的作用。我们发现，虽然EGF刺激MDA-MB-468细胞中GFAT mRNA的积累，但EGF的这种作用在TGF-α转录增加数小时后才出现。MDA-MB-468细胞对低浓度葡萄糖也表现出TGF-α转录反应。GFAT活性阻滞剂可抑制TGF-α对葡萄糖而非EGF的反应。通过使用识别含N-乙酰葡糖胺蛋白质上一个表位的RL2抗体进行蛋白质印迹法证实了GFAT的阻断。细胞暴露于葡萄糖会增加几种多肽上的RL2信号，但这种变化可被GFAT抑制所阻断。这些结果支持以下观点，即葡萄糖刺激TGF-α表达需要GFAT，而EGF刺激则不需要。
