Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology and Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Währinger Gürtel, 18-20A-1090 Vienna, Austria.
Medical University of Vienna, Department of Internal Medicine III, Division of Gastroenterology and Hepatology and Christian Doppler Laboratory for Molecular Cancer Chemoprevention, Währinger Gürtel, 18-20A-1090 Vienna, Austria.
Biochem Pharmacol. 2014 Jan 15;87(2):312-20. doi: 10.1016/j.bcp.2013.10.021. Epub 2013 Oct 30.
Genome wide association studies have implicated intestinal barrier function genes in the pathogenesis of ulcerative colitis. One of such loci CDH1, encoding E-cadherin, a transmembrane glycoprotein with known tumor suppressor functions, is also linked to the susceptibility to colorectal cancer. Loss of membranous E-cadherin expression is common in both colitis and cancer. We have recently demonstrated that mesalamine (5-ASA); the anti-inflammatory drug used to treat ulcerative colitis, induces membranous expression of E-cadherin and increases intercellular adhesion. Using colorectal cancer epithelial cells with aberrant E-cadherin expression, we investigated the mechanism underlying such an effect of 5-ASA. Post-translational modification of E-cadherin glycosylation was analyzed by biotin/streptavidin detection of sialylated glycoproteins. GnT-III (N-acetylglucosaminyltransferase III) expression was assessed by qRT-PCR, Western blot and immunofluorescence. GnT-III activity was analyzed by reactivity with E-4/L-4-PHA. Expression, localization and interaction of E-cadherin and β-catenin were analyzed by Western blot, immunocytochemistry and RNA interference. 5-ASA activity modulated E-cadherin glycosylation and increased both mRNA and protein levels of GnT-III and its activity as detected by increased E4-lectin reactivity. Intestinal APC(Min) polyps in mice showed low expression of GnT-III and 5-ASA was effective in increasing its expression. The data demonstrated that remodeling of glycans by GnT-III mediated bisect glycosylation, contributes to the membranous retention of E-cadherin by 5-ASA; facilitating intercellular adhesion. Induction of membranous expression of E-cadherin by 5-ASA is a novel mechanism for mucosal healing in colitis that might impede tumor progression by modulation of GnT-III expression.
全基因组关联研究表明，肠屏障功能基因在溃疡性结肠炎的发病机制中起作用。其中一个位点 CDH1 编码 E-钙黏蛋白，是一种具有已知肿瘤抑制功能的跨膜糖蛋白，也与结直肠癌的易感性有关。膜 E-钙黏蛋白表达的丧失在结肠炎和癌症中都很常见。我们最近的研究表明，美沙拉嗪（5-ASA），一种用于治疗溃疡性结肠炎的抗炎药物，可诱导 E-钙黏蛋白的膜表达，并增加细胞间的黏附。使用具有异常 E-钙黏蛋白表达的结直肠癌细胞，我们研究了 5-ASA 产生这种作用的机制。通过生物素/链霉亲和素检测唾液酸化糖蛋白分析 E-钙黏蛋白糖基化的翻译后修饰。通过 qRT-PCR、Western blot 和免疫荧光分析 GnT-III（N-乙酰氨基葡萄糖转移酶 III）的表达。通过与 E-4/L-4-PHA 的反应性分析 GnT-III 活性。通过 Western blot、免疫细胞化学和 RNA 干扰分析 E-钙黏蛋白和 β-连环蛋白的表达、定位和相互作用。5-ASA 活性调节 E-钙黏蛋白糖基化，并增加 GnT-III 的 mRNA 和蛋白水平及其活性，如通过增加 E4-凝集素反应性检测到的。在小鼠的肠道 APC(Min)息肉中，GnT-III 的表达较低，而 5-ASA 能有效增加其表达。这些数据表明，GnT-III 介导的双糖苷基化修饰糖链，有助于 5-ASA 保留 E-钙黏蛋白的膜表达，促进细胞间黏附。5-ASA 诱导 E-钙黏蛋白的膜表达是结肠炎黏膜愈合的一种新机制，通过调节 GnT-III 的表达可能会阻碍肿瘤的进展。
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