ROLE OF N-LINKED GLYCANS AND PROTEIN FOLDING

蛋白质折叠是一个基本的，但仍然知之甚少的过程， 活细胞本申请中提出的实验设计 评估折叠领域新概念的分子基础： N-连接聚糖作为伴侣结合的附属物的直接作用 糖蛋白在内质网中折叠和组装的过程中。初步结果 表明钙连接蛋白，一种普遍存在的ER伴侣，与其 通过凝集素样亲和力与部分葡萄糖修饰的N-连接的 低聚糖（Glc 1 Man 9 - 7 GlcNAc 2）。对于许多糖蛋白， 联合（由葡萄糖氧化酶和内腔UDP调节， Glc：糖蛋白葡糖基转移酶）可能决定 折叠和输出到高尔基复合体的效率。 我们的总体目标是分析钙连接蛋白的作用及其可溶性 同源钙网蛋白的构象成熟和质量 控制新合成的糖蛋白。我们将分析 糖蛋白与钙连接蛋白结合的特异性和结构基础， 钙网蛋白，ER腔中的可溶性同源物。我们还将确定 钙连接蛋白和钙网蛋白联合的功能意义 在糖蛋白生物合成中。最后，我们将研究UDP的作用- 葡萄糖：糖蛋白葡萄糖基转移酶，及其机制 在内质网支持的再糖基化和去糖基化循环中。的 实验将利用生物化学、细胞生物学、遗传学和 结构方法。 这些结果将有助于阐明各种生物学行为的机制。 糖蛋白获得其运输能力的三维 活细胞ER中的结构。结果将直接 与ER储存/质量控制的各种疾病相关 病因包括囊性纤维化和α 1-抗胰蛋白酶缺乏。的 对核心聚糖的共翻译糖基化和修剪的需要可能， 此外，在糖基化和糖基化之间的联系中找到他们的解释。 折叠、低聚物组装、降解和质量控制。

Protein folding is a fundamental but still poorly understood process in living cells. The experiments proposed in this application are designed to evaluate the molecular basis of a novel concept in the folding field: the direct role of N-linked glycans as appendages for chaperone-binding during glycoprotein folding and assembly in the ER. Preliminary results indicate that calnexin, a ubiquitous ER chaperone, associates with its ligands by lectin-like affinity to partially glucose-trimmed N-linked oligosaccharides(Glc1Man9-7GlcNAc2). For many glycoproteins, this association (modulated by glucosidases and the lumenal UDP- Glc:glycoprotein glucosyltransferase) is likely to determine the rate of folding and the efficiency of export to the Golgi complex. Our overall goal is to analyze the role of calnexin and its soluble homologue calreticulin in the conformational maturation and quality control of newly synthesized glycoproteins. We will analyze the specificity and structural basis for glycoprotein binding to calnexin and calreticulin, a soluble homologue in the ER lumen. We will also determine the functional significance of the calnexin and calreticulin association in glycoprotein biogenesis. Finally, we will investigate the role of UDP- glucose: glycoprotein glucosyl transferase, and the mechanisms involved in the re-and deglucosylation cycle that it supports in the ER. The experiments will utilize biochemical, cell biological, genetic and structural approaches. The results will throw light on the mechanisms by which a variety of glycoproteins acquire heir transport-competent three-dimensional structure in the ER of living cell. The results will have direct relevance to a variety of diseases with ER storage/quality control etiology including cystic fibrosis and alpha1-antitrypsin deficiency. The need for cotranslational glycosylation and trimming of core glycans may, moreover, find their explanation in the link between glycosylation and folding, oligomeric assembly, degradation and quality control.