Department of Biochemistry & Molecular Biology, Division of Biological Sciences, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, Japan.
Biochem Biophys Res Commun. 2012 Jan 6;417(1):364-70. doi: 10.1016/j.bbrc.2011.11.118. Epub 2011 Dec 1.
To identify molecular targets associated with the development of diabetes, we analyzed the hepatic proteome of obese diabetic db/db mice using electrophoresis on a high-resolution two-dimensional gel combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. By comparison between non-diabetic db/+ and diabetic db/db mice, six proteins and one protein were significantly decreased and increased in the diabetic mice, respectively. Among these proteins, two of the decreased proteins are involved in endoplasmic reticulum (ER) stress-related unfolded protein response, GRP78 and protein disulfide isomerase A3, and it was revealed that the decreased GRP78 expression in the liver of diabetic db/db mice is due to the reduction of GRP78 protein synthesis rather than RNA transcription. In addition, we found that the treatment of human hepatocyte HepG2 cells with oleic acid decreased the expression of GRP78, and attenuated the activation of AKT by insulin stimulation. These results suggest that decreased GRP78 expression may induce resistance to insulin by inhibiting the AKT activation, and plays an important role in the development of type 2 diabetes.
为了鉴定与糖尿病发生相关的分子靶标，我们应用高分辨率二维电泳联合基质辅助激光解吸电离飞行时间质谱分析肥胖型糖尿病 db/db 小鼠的肝蛋白质组，通过比较非糖尿病 db/+和糖尿病 db/db 小鼠，我们发现 6 种蛋白在糖尿病 db/db 小鼠中显著减少，1 种蛋白显著增加。在这些蛋白中，2 种减少的蛋白与内质网（ER）应激相关的未折叠蛋白反应有关，分别为 GRP78 和蛋白二硫键异构酶 A3。结果显示，糖尿病 db/db 小鼠肝脏中 GRP78 表达减少是由于 GRP78 蛋白合成减少而不是 RNA 转录减少所致。此外，我们发现油酸处理人肝癌 HepG2 细胞可降低 GRP78 的表达，并减弱胰岛素刺激引起的 AKT 激活。这些结果提示，GRP78 表达减少可能通过抑制 AKT 激活而导致胰岛素抵抗，并在 2 型糖尿病的发生发展中发挥重要作用。
