Homogeneous Heparan Sulfate Glycopeptides: Synthetic and Functional Studies

 描述(由申请人提供)：硫酸乙酰肝素蛋白多糖(HSPGs)在许多生物学事件中发挥重要作用，包括淀粉样斑块形成、病毒感染、炎症和癌症发展。由于硫酸乙酰肝素侧链结构的多样性，从自然界中分离出来的HSPG是一种高度非均相的混合物。传统上认为，硫酸乙酰肝素决定了HSPG的功能。最近的研究已经获得越来越多的证据，表明糖链和核心多肽/蛋白质都可能是关键的。因此，为了彻底了解它们的功能，重要的是能够获得含有均一多聚糖的HSPG。然而，到目前为止，还没有通用的合成方法来制备这种类型的结构。为了克服这一障碍，在这一应用中，将开发新的方法来合成这些具有高度挑战性的分子，然后将用于了解HSPG如何与淀粉样β相互作用。这个应用程序有四个目标。在目标1中，将建立一种化学合成策略，用于含一条乙酰肝素硫酸酯链的HSPG糖肽。发展了合适的保护基团和糖基化化学，证明了化学合成含一条糖链的HSPG糖肽的可行性。在目标2中，将建立一种不同的方法来用硫酸乙酰肝素生物合成酶修饰HSPG糖肽。有希望的初步结果表明，酶合成可以很好地与化学合成相结合，使从一个共同的中间体制备具有不同糖链结构的糖肽成为可能。在目标3中，通过化学和酶法相结合的方法，将生产出含有多个糖链和延伸的肽骨架的HSPG糖肽。这将导致糖肽接近HSPGs的全部复杂性。在目标4中，使用合成的硫酸乙酰肝素/热休克蛋白糖肽，将确定它们与阿尔茨海默病的病理标志--淀粉样β相互作用的关键结构特征。拟议的研究将提供前所未有的途径获得含有均一硫酸乙酰肝素多糖的热休克蛋白，这将为研究其令人兴奋的生物学特性提供令人兴奋的机会。

 DESCRIPTION (provided by applicant): Heparan sulfate proteoglycans (HSPGs) play important roles in many biological events including amyloid plaque formation, viral infection, inflammation, and cancer development. HSPGs isolated from nature exist as a highly heterogeneous mixture due to the variable structures of the heparan sulfate side chains. Heparan sulfates are traditionally believed to dictate the functions of HSPGs. Recent studies have gained increasing evidence suggesting that both the glycan chains and the core peptides/proteins can be critical. Therefore, to thoroughly understand their functions, it is important to have access to HSPGs bearing homogeneous glycans. However, to date, no general synthetic methodologies are available to prepare this type of structures. In order to overcome this obstacle, in this application, novel methodologies will be developed to synthesize these highly challenging molecules, which will then be used to understand how HSPGs interact with amyloid ß. There are four aims in this application. In aim 1, a chemical synthesis strategy will be established towards HSPG glycopeptides bearing one heparan sulfate chain. Suitable protective group and glycosylation chemistry has been developed demonstrating the feasibility of chemically synthesizing HSPG glycopeptides with one glycan chain. In aim 2, a divergent approach will be established to modify HSPG glycopeptides with heparan sulfate biosynthetic enzymes. Promising preliminary results have been obtained suggesting enzymatic synthesis can be well integrated with chemical synthesis to enable the preparation of glycopeptides with diverse glycan structures from a common intermediate. In aim 3, through a combination of chemical and enzymatic methods, HSPG glycopeptides bearing multiple glycan chains and extended peptide backbone will be produced. This will lead to glycopeptides approaching the full complexities of HSPGs. In aim 4, using the synthetic heparan sulfate/HSPG glycopeptides, the structural features critical for their interactions with amyloid ß, the pathological hallmark f Alzheimer's disease, will be identified. The proposed studies will provide the unprecedented access to HSPGs containing homogeneous heparan sulfate glycans, which will lead to exciting opportunities for studies of their fascinating biological properties.