N-Glycosylation And ER Stress

分泌的许多至关重要的蛋白质(如免疫球蛋白和多肽激素) 或存在于细胞表面(包括细胞黏附分子和信号受体)，并 由内质网(ER)折叠。如果内质网折叠这些蛋白质有问题，一个代偿性的内质网 应激反应(又名未折叠蛋白反应)被触发以增强各种内质网相关折叠 流程。内质网产生的蛋白质经常被天冬酰胺结合的糖聚合物N-糖基化 (多聚糖)。这些多糖密切参与N-糖蛋白的折叠，也可以参与它们的 在分泌或到达细胞表面后起作用。内质网相关脂联寡糖(LLO) Glc3Man9GlcNAc2-P-P-dolicol提供用于制造N-糖蛋白的糖(Glc3Man9GlcNAc2)。那里 有13种人类遗传性疾病(其中12种无法治愈)，即先天性糖基化紊乱(CDG-I) Ia-Im型，LLO合成缺陷。因此，CDG-I细胞由于糖基化不良而出现内质网功能障碍， 而且患者在临床上有很多困难。这项研究计划探索P.I.S的发现 LLO的合成是内质网应激反应调节的过程之一，他的假设是 反应可以在药理学上被用于修复CDG-I中LLO合成的异常。因此 这项拨款的研究将P.I.带入了一个新的视角，在这个视角下，G3M9Gn2-P-P-Dol的生产 不是作为一个硬连接的过程，而是一个不断监测和调整的过程。Aim我会研究一下 内质网应激反应作为核糖核酸水平的重要调节因子，其生化前体 多聚糖。AIM II将使用CDG-I培养模型来测试与药物相关的内质网应激 调节剂可以抵消LLO合成缺陷，以及某些CDG-I患者的LLO功能障碍 被内源性触发的内质网应激反应纠正。AIMS III和IMS IV将提供重要的新 有关甘露糖-6-磷酸(M6P)意外活性的信息。私家侦探发现M6P是 由内质网应激引起，并导致Glc3Man9GlcNAc2-P-P-Dolicol释放多糖。AIM III将 开发定制合成的M6P类似物，以阐明其细胞作用。AIM IV将探讨 内质网动态平衡中M6P释放的多糖。这项研究的临床相关性是双重的。第一，新 将评估治疗糖基化缺陷人类疾病的策略，包括现有的一些 毒品。其次，这项工作将产生关于内质网应激反应的新信息，这一信息支配着 内质网的生产力对于浆细胞(免疫球蛋白)和胰腺的分泌功能是必不可少的 胰岛(胰岛素)，当控制异常时会导致神经系统疾病，胆固醇失衡，以及 肥胖。

Many vitally important proteins which are secreted (such as immunoglobulins and polypeptide hormones) or present at the cell surface (including cell adhesion molecules and signaling receptors) are produced and folded by the endoplasmic reticulum (ER). If the ER has problems folding these proteins, a compensatory ¿ER stress response¿ (a.k.a. Unfolded Protein Response) is triggered to enhance various ER-related folding processes. ER-produced proteins are frequently N-glycosylated with asparagine-bound sugar polymers (glycans). The glycans are intimately involved in folding of N-glycoproteins, and can also participate in their functions after secretion or reaching the cell surface. The ER-associated lipid-linked oligosaccharide (LLO) Glc3Man9GlcNAc2-P-P-dolichol provides the glycan (Glc3Man9GlcNAc2) used to make N-glycoproteins. There are 13 human genetic diseases (12 are untreatable), the ¿Congenital Disorders Of Glycosylation¿ (CDG-I) Types Ia-Im, with defective LLO synthesis. Thus, CDG-I cells have ER dysfunction due to poor Nglycosylation, and patients have many clinical difficulties. This research proposal explores the P.I.¿s discovery that LLO synthesis is one of the processes regulated by the ER stress response, and his hypothesis that the response can be co-opted pharmacologically to repair LLO synthesis abnormalities in CDG-I. Consequently research with this grant has led the P.I. to a new perspective, in which G3M9Gn2-P-P-Dol production is viewed not as a hard-wired process, but rather one which is constantly monitored and adjusted. AIM I will examine the ER stress response as an important regulator of levels of nucleotide-sugars, the biochemical precursors of glycans. AIM II will use CDG-I culture models to test whether pharmacologically-relevant ER stress modulators can counteract LLO synthesis defects, and whether LLO dysfunction in some CDG-I patients¿ cells is corrected by endogenously-triggered ER stress responses. AIMS III and IV will provide important new information about an unexpected activity of mannose-6-phosphate (M6P). The P.I. discovered that M6P is elevated by ER stress, and causes release of the glycan from Glc3Man9GlcNAc2-P-P-dolichol. AIM III will develop custom-synthesized analogues of M6P to elucidate its cellular action. AIM IV will explore the role of M6P-released glycans in ER homeostasis. The clinical relevance of this research is two-fold. First, new strategies for treating glycosylation-deficient human diseases will be evaluated, including some with existing drugs. Second, this work will generate new information about the ER stress response, which governs the productivity of the ER, is essential for the secretory functions of plasma cells (immunoglobulins) and pancreatic islets (insulin), and when aberrantly controlled can cause neurological diseases, cholesterol imbalance, and obesity.