Studies of O-linked Glycosylation

描述(申请人提供)：本项目的目标是：(1)开发用于基础研究O-连接糖基化的化学工具，以及(2)鉴定糖蛋白癌症生物标记物。粘蛋白-O-连接糖基化是高等真核生物膜蛋白和分泌蛋白的翻译后修饰。它的功能知之甚少，但改变的粘蛋白O连接的糖基化与肿瘤的生长和转移有关。需要化学工具来干扰和检测蛋白质和细胞上的O-连接糖基化。这一新应用的第一个主要目标是通过靶向多肽N-乙酰半乳糖胺转移酶(PpGalNActs)和UDP-GlcNAc/GalNAc C4-差向异构酶(Gale)，开发粘蛋白O-连接糖基化的小分子抑制剂。这些抑制剂将被用来探索O-连接多糖在肿瘤生长和转移中的重要性。第二个目标是开发一种化学方法，用于快速分析与癌症相关的粘蛋白O型连接糖基化的变化。该方法包括使用N-乙酰半乳糖胺的叠氮类似物(称为GalNAz)在活体动物体内对O连接的糖蛋白进行代谢标记。来自血清和组织样本的标记糖蛋白将通过Staudinger连接用膦探针进行化学标记，从而允许使用蛋白质组学方法检测和鉴定它们。比较正常小鼠和荷瘤小鼠的标记物种，可能会发现新的疾病血清生物标志物。最终目标是开发一种类似的方法来检测蛋白质O-岩藻糖基化，这是一种最近发现的具有神秘功能的O-连接糖基化形式。已知细胞表面糖参与许多正常和疾病过程，但尚未被用作药物或临床诊断的靶点。这项研究将促进我们对细胞表面糖在肿瘤生长和转移中所起作用的理解。该项目开发的化学工具可能会生产出新一代抗癌药物和新的临床测试，用于早期诊断。

DESCRIPTION (provided by applicant): The objectives of this project are: (1) the development of chemical tools for fundamental studies of O-linked glycosylation, and (2) the identification of glycoprotein cancer biomarkers. Mucin-type O-linked glycosylation is a posttranslational modification of membrane and secreted proteins in higher eukaryotes. Its functions are poorly understood, but altered mucin-type O-linked glycosylation has been correlated with cancer growth and metastasis. Chemical tools are needed both for perturbing and detecting O-linked glycosylation on proteins and cells. The first major goal of this renewal application is to develop small molecule inhibitors of mucin-type O-linked glycosylation by targeting the polypeptide N-acetylgalactosaminyltransferases (ppGalNAcTs) and UDP-GlcNAc/GalNAc C4-epimerase (GALE), enzymes that are required for O-glycan biosynthesis. The inhibitors will be used to probe the importance of O-linked glycans in tumor growth and metastasis. The second goal is to develop a chemical approach for rapid profiling of changes in mucin-type O-linked glycosylation associated with cancer. The approach involves metabolic labeling of O-linked glycoproteins within living animals using an azido analog of N-acetylgalactosamine (termed GalNAz). The labeled glycoproteins from serum and tissue samples will be chemically tagged with phosphine probes via Staudinger ligation, permitting their detection and identification using proteomic methods. Comparison of labeled species from normal and tumor-bearing mice may reveal new serum biomarkers of disease. The final goal is to develop an analogous method for detection of protein O-fucosylation, a recently discovered form of O-linked glycosylation with mysterious functions. Cell-surface sugars are known to participate in many normal and disease processes, but have not yet been exploited as targets for drugs or clinical diagnostics. This research will advance our understanding of the roles cell-surface sugars play in tumor growth and metastasis. The chemical tools developed in this project may produce a new generation of anti-cancer drugs and new clinical tests for early diagnosis.