The molecular basis and functional consequences of IgG subclass glycosylation

与蛋白质相关的碳水化合物（聚糖）在生活的许多方面起着至关重要的作用。然而，它们对糖蛋白功能的确切影响和潜在的分子机制知之甚少，主要是由于它们巨大的结构变异性和复杂性。这些特征使得预测聚糖的结构-功能关系在概念上具有挑战性，令人满意的解决方案尚未确定。各种国际组织（如欧洲糖苷科学论坛，美国国家研究委员会）独立地建议，必须作出实质性的努力，以提高我们对蛋白质-碳水化合物相互作用的理解。实现这一目标的一个重要先决条件是控制聚糖生物合成的能力。因此，对细胞和表达宿主进行糖工程以实现对糖蛋白产生的严格控制是当前和未来研究的重要内容。理解差异蛋白糖基化的功能后果的另一个挑战，特别是对人体系统来说，是只有非常有限数量的模型系统可用，允许在糖科学框架内放置免疫学/医学数据，反之亦然。事实上，整合互补的科学学科是必要的，以充分利用蛋白连接聚糖的独特性质，并评估其未来治疗方法的潜力。通过整合维也纳的Steinkellner教授和埃尔兰根的Nimmerjahn教授的独特专业知识，本研究计划试图克服这些挑战。我们将重点关注人类抗体，这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，将生成所有人IgG亚类的高度定义的糖变体，这也将允许获得蛋白质糖基化途径的基本见解。此外，在体外和新的人源化小鼠模型系统将用于鉴定体内抗体活性的糖基化依赖性改变。

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.