Development of Biochemical Tools and Approaches for Studying Siglecs

四种主要类型的生物分子组成活细胞：蛋白质、核酸、脂类和低聚糖。其中，寡糖也被称为多糖，是唯一一种不存在自组装(脂类)或模板驱动的生物合成(蛋白质和DNA/RNA)的类型。相反，多糖的组装是由酶的连续作用以空间和时间控制的方式控制的。由于这个原因和其他原因，多糖在化学和生物化学上是复杂的，这使得他们的研究本身就具有挑战性。因此，操纵糖链的工具落后于相对成熟的操纵遗传密码的方法。因此，有相当大的机会开发创新的战略来分析和操纵细胞多糖；事实上，新的工具将使研究多糖生物学作用的广泛科学家受益。多糖的一个关键作用是在免疫系统中，因为它们被白细胞上表达的大量糖结合蛋白(GBP)识别为配体。虽然GBP-葡聚糖相互作用的许多功能在免疫细胞上已被描述，但关于这些相互作用控制免疫细胞功能的潜在机制仍有许多需要了解。我的实验室研究的是GBP的Siglec(唾液酸结合免疫球蛋白类型凝集素)家族，它含有高度复杂的葡聚糖配体。Siglecs具有免疫调节特性，通过与其糖链配体的相互作用来调节。只有通过开发新的方法来分析和调节Siglecs的糖链配体，才能充分了解Siglecs控制免疫细胞功能的机制。在这项研究计划中，我们将提出多种互补的方法来解剖Siglec的葡聚糖配体(例如，质谱学、流式细胞术和脂质体纳米粒)，并反过来开发化学工具来操纵这些葡聚糖。利用化学生物学方法和尖端基因组编辑的协同组合，总体目标是开发可用于询问Siglecs调节免疫细胞功能的策略，可应用于更广泛的研究GBP角色的研究科学家社区。

Four major types of biomolecules make up living cells: proteins, nucleic acids, lipids, and oligosaccharides. Of these, oligosaccharides also known as glycans are the only type in which there is no self-assembly (lipids) or template-driven biosynthesis (protein and DNA/RNA). Instead, the assembly of glycans is controlled by the successive actions of enzymes in a spatially- and temporally-controlled manner. For this reason, and others, glycans are chemically and biochemically complex, making their study inherently challenging. Consequently, tools that manipulate glycans lag behind the comparatively well-establish methodologies of manipulating the genetic code. Accordingly, there is considerable opportunity for developing innovative strategies to analyze and manipulate cellular glycans; indeed, new tools would benefit a broad range of scientists studying the biological roles for glycans. One key role of glycans is within the immune system as they are recognized as ligands by a plethora of glycan-binding proteins (GBPs) expressed on white blood cells. While many functions for GBP-glycan interactions have been described on immune cells, there is still much to be learned about the underlying mechanisms through which these interactions control immune cell function. My lab studies the Siglec (sialic acid-binding immunoglobulin-type lectin) family of GBPs which contains glycan ligands that are highly complex. Siglecs have immunomodulatory properties, which are regulated by interactions with their glycan ligands. Understanding the mechanisms by which Siglecs control immune cell function can only be fully realized by developing new approaches to analyze and modulate their glycan ligands. In this program of research, we will advance a variety of complementary approaches for dissecting glycan ligands for Siglec (e.g. mass spectrometry, flow cytometry, and liposomal nanoparticles) and, in turn, develop chemical tools to manipulate these glycans. Using a synergistic combination of chemical biology approaches and cutting-edge genome editing, the overall objective is to develop strategies that can be used for interrogating the function of Siglecs regulating immune cell function, which can be applied to the wider community of research scientists studying the roles of GBPs.