Department of Molecular Biochemistry and Clinical Investigation, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan.
Int J Oncol. 2011 Jul;39(1):203-8. doi: 10.3892/ijo.2011.1005. Epub 2011 Apr 14.
Golgi phosphoprotein 2 (GP73) is a type II Golgi protein, which was found on examination of the fucosylated proteome as a potential tumor marker for hepatocellular carcinoma (HCC). The serum levels of both total and fucosylated GP73 were increased in the sera of patients with HCC. Fucosylation is one of the most important oligosaccharide modifications involved in cancer and is catalyzed by α1,6-fucosyltransferase (Fut8). In the present study, we investigated the effect of Fut8 overexpression on GP73 production in the human hepatoma cell line Hep3B. The Fut8 expression vector was transfected into Hep3B cells and the expression of GP73 was investigated by Western blotting and real-time PCR. Overexpression of Fut8 dramatically enhanced the expression of GP73 at the transcriptional level. Surprisingly, this effect was not dependent on cellular fucosylation. Overexpression of a mutant Fut8, which was unable to be localized to the Golgi, did not induce GP73 production, suggesting that the localization of Fut8 in the Golgi apparatus was important for the increase in GP73 expression. This is the first demonstration of GP73 regulation through overexpression of a glycosyltransferase, which may lead to Golgi stress.
高尔基糖蛋白 2 (GP73) 是一种 II 型高尔基蛋白，在对岩藻糖基化蛋白质组进行检查时，被发现是肝细胞癌 (HCC) 的潜在肿瘤标志物。HCC 患者血清中总 GP73 和岩藻糖基化 GP73 的水平均升高。糖基化是癌症中最重要的寡糖修饰之一，由α1,6-岩藻糖基转移酶 (Fut8) 催化。在本研究中，我们研究了 Fut8 过表达对人肝癌细胞系 Hep3B 中 GP73 产生的影响。将 Fut8 表达载体转染到 Hep3B 细胞中，并通过 Western blot 和实时 PCR 研究 GP73 的表达。Fut8 的过表达在转录水平上显著增强了 GP73 的表达。令人惊讶的是，这种效应不依赖于细胞岩藻糖基化。过表达一种不能定位于高尔基体的突变 Fut8 不会诱导 GP73 产生，这表明 Fut8 在高尔基体中的定位对于 GP73 表达的增加很重要。这是首次通过糖基转移酶的过表达来调节 GP73，这可能导致高尔基体应激。
