The molecular basis and functional consequences of IgG subclass glycosylation

与蛋白质相连的碳水化合物(糖类)在生活的许多方面都扮演着重要的角色。然而，它们对糖蛋白功能的确切影响和潜在的分子机制还知之甚少，主要是因为它们具有巨大的结构多样性和复杂性。这些特征使得预测多聚糖的结构-功能关系在概念上是一项具有挑战性的任务，目前还没有确定满意的解决方案。不同的国际组织(如欧洲糖科学论坛、美国国家研究委员会)独立地建议，必须做出大量努力来提高我们对蛋白质-碳水化合物相互作用的理解。实现这一目标的一个重要前提是能够控制多糖的生物合成。因此，对细胞和表达宿主进行糖工程以实现对糖蛋白生产的严格控制对于当前和未来的研究是至关重要的。在理解差异蛋白质糖基化的功能后果方面，特别是对人类系统来说，另一个挑战是，只有非常有限的模型系统可用，允许将免疫学/医学数据置于糖科学框架内，反之亦然。事实上，为了充分利用蛋白质连接的葡聚糖的独特性质，并评估其未来治疗方法的潜力，互补的科学学科的整合是强制性的。通过整合维也纳的Steinkellner教授和Erlangen的Nimerjahn教授的独特专业知识，本研究提案试图克服这些挑战。我们将关注人类抗体，它是高度可变的糖蛋白，是免疫系统的重要组成部分。通过使用植物蛋白生产系统，将产生所有人类免疫球蛋白亚类的高度定义的糖变异体，这也将允许获得对蛋白质糖基化途径的基本见解。此外，体外和新型人源化小鼠模型系统将被用来识别体内抗体活性中依赖糖基化的变化。

Carbohydrates (glycans) linked to proteins play essential roles in many aspects of life. However, their precise impacts on glycoprotein function and underlying molecular mechanisms are poorly understood, mainly due to their enormous structural variability and complexity. These features render the prediction of structure-function relationships of glycans a conceptually challenging task for which satisfying solutions have not yet been determined. Various international organizations (e.g. Euroglycoscience Forum, US National Research Council) independently recommend that substantial efforts have to be undertaken to improve our understanding of protein-carbohydrate interactions. An important prerequisite for this objective is the ability to control glycan biosynthesis. Thus glycoengineering of cells and expression hosts to achieve tight control of glycoprotein production are paramount for current and future investigations. An additional challenge in understanding the functional consequences of differential protein glycosylation especially for the human system is the fact that only a very limited number of model systems are available, allowing to place immunological/medical data within the framework of glycoscience, and vice versa. Indeed, integration of complementary scientific disciplines is mandatory to fully exploit the unique properties of protein linked glycans, and to evaluate their potential for future therapeutic approaches. By integrating the unique expertise of the group of Prof. Steinkellner in Vienna and Prof. Nimmerjahn in Erlangen, this research proposal tries to overcome these challenges. We will focus on human antibodies, which are highly variable glycoproteins and are an essential part of the immune system. By using a plant protein production system highly defined glycovariants of all human IgG subclasses will be generated which will also allow to obtain basic insights into the pathways of protein glycosylation. In addition, in vitro and novel humanized mouse model systems will be used to identify glycosylation dependent alterations in antibody activity in vivo.