Chemical tools for studying fucosylated glycans

性状（由申请方提供）：岩藻糖基化聚糖广泛分布于真核生物和某些细菌中。在哺乳动物细胞表面，它们介导多种生理和病理过程，包括血管生成、受精、胚胎发生、炎症和肿瘤转移。在病原菌和寄生虫中，岩藻糖苷调节宿主组织的粘附和定殖，并调节宿主免疫应答。尽管岩藻糖基化聚糖的重要性显而易见，但其结构复杂性和异质性严重阻碍了对其功能的分子基础的描述。目前，还没有简便且具有成本效益的化学方法来合成这些聚糖及其结构相关的衍生物。该项目的长期目标是开发用于制备结构确定的岩藻糖苷及其衍生物的新方法，并制造用于全面探索岩藻糖苷-蛋白质相互作用的新聚糖阵列平台。 在第一个资助阶段，我们将专注于三个具体目标。首先，我们将开发一种通用的化学酶促策略，用于通用岩藻糖基供体，胍52-二磷酸-2-L-岩藻糖（GDP-岩藻糖），以及化学定义的岩藻糖苷及其结构相关的衍生物的化学规模合成。我们将利用细菌来源的岩藻糖基活化和转移酶来合成岩藻糖基化聚糖和糖缀合物，用于其功能研究。 使用目标1中生成的岩藻糖苷库，我们将制备磷脂缀合的glycodendrimers的库，并将其以微阵列形式纳入支持的脂质双层膜中（目标2）。平面脂质双层中聚糖的流体性质与多价显示相结合，与当今大多数阵列中发现的常规固定化单体聚糖相比，更好地反映了自然界中发现的聚糖的呈现。获得结构上确定的岩藻糖苷结合糖树枝状聚合物微阵列技术提供了一个强大的，快速的手段来配置文件岩藻糖苷-蛋白质相互作用，并确定关键的结构特征有助于结合。在目标3中，我们将使用这种技术来鉴定非天然的刘易斯X衍生物，其对DC-SIGN（树突状细胞特异性ICAM-3抓取非整合素）具有增强的亲合力，DC-SIGN是一种重要的内吞受体介导的抗原呈递。将在体外测试从本研究中鉴定的具有增强的DC-SIGN亲合力的聚糖配体作为用于将货物递送至树突细胞的靶向元件。 公共卫生相关性：岩藻糖基化聚糖存在于细胞表面，在正常生物学过程和人类疾病中参与的细胞间相互作用中发挥关键作用。本研究的目的是开发用于研究岩藻糖基化聚糖和糖缀合物的生物学功能的化学工具。这些工具将提高我们对这些重要聚糖如何导致癌症和炎症等疾病的理解。

DESCRIPTION (provided by applicant): Fucosylated glycans are widely distributed throughout eukaryotes and certain bacteria. On the surface of mammalian cells, they mediate a variety of physiological and pathological processes, including angiogenesis, fertilization, embryogenesis, inflammation, and tumor metastasis. In pathogenic bacteria and parasites, fucosides regulate adhesion and colonization of host tissues and modulate the host immune response. Despite the obvious importance of fucosylated glycans, delineating the molecular basis of their function is severely hampered by their structural complexity and heterogeneity. Currently, there is no facile and cost-effective chemistry for synthesizing these glycans and their structurally related derivatives. The long term goal of this project is to develop new methods for the preparation of structurally defined fucosides and their derivatives and to fabricate new glycan array platforms for the comprehensive exploration of fucoside- protein interactions. In the first granting period, we will focus on three specific aims. First, we will develop a general chemoenzymatic strategy for preparative-scale synthesis of the universal fucosyl donor, guanidine 52- diphosphate-2-L-fucose (GDP-fucose), as well as chemically defined fucosides and their structurally related derivatives. We will harness fucosyl activation and transfer enzymes from bacterial sources to synthesize fucosylated glycans and glycoconjugates for their functional studies. Using the fucoside libraries generated in Aim 1, we will prepare a library of phospholipid-conjugated glycodendrimers and incorporate them into supported lipid bilayer membranes in a microarray format (Aim 2). The fluid nature of glycans in the planar lipid bilayer, coupled with the multivalent display, better mirrors the presentation of glycans found in nature as compared to the conventional immobilized monomeric glycans found in most arrays today. Access to structurally defined fucosides combined with the glycodendrimer microarray technology provides a powerful, rapid means to profile fucoside-protein interactions and to identify key structural features contributing to binding. In Aim 3, we will use this technology to identify unnatural Lewis X derivatives with enhanced avidity for DC-SIGN (dendritic cell-specific ICAM-3-grabbing nonintegrin), an important endocytic receptor mediating antigen presentation. The glycan ligands with enhanced DC-SIGN avidity identified from this study will be tested in vitro as targeting elements for delivering cargos to dendritic cells. PUBLIC HEALTH RELEVANCE: Fucosylated glycans are found on cell surfaces, where they play key roles in cell-cell interactions involved in normal biological processes and also in human disease. The goal of this research is to develop chemical tools for studying the biological functions of fucosylated glycans and glycoconjugates. These tools will improve our understanding of how these important glycans contribute to diseases such as cancer and inflammation.