Sialyl transferase function in vascular biology

将唾液酸转移到糖蛋白和糖脂的酶称为唾液酸转移酶。唾液酸的添加通常终止进一步的寡糖生物合成，从而可以产生并掩盖生物学相关的聚糖结构。 在脊椎动物中，存在高度保守的唾液酸转移酶基因家族，其包含至少18个成员。 这些基因表现出的表达谱通常是发育限制和细胞或 组织类型特异性。从有限的研究，迄今为止，唾液酸连接已被发现调节细胞运输，粘附，糖蛋白在血浆中的半衰期，和涉及多亚基受体复合物的信号转导。在体内确定唾液酸转移酶基因功能时，使用Cre-loxP定点重组在胚胎干细胞和成年小鼠中产生小鼠生殖系突变。 随后，通过使用本计划项目赠款提供的特定表型核心设施评估生理参数。以这种方式，我们以前的研究结果已经建立了特定的唾液酸转移酶基因的关键止血和免疫作用。例如，ST 3Gal-I和ST 3Gal-IV促进血小板稳态，而ST 3Gal-IV缺乏特异性地导致小鼠中的常染色体显性遗传性yon Willebrand病样综合征。 该项目的目标是进一步阐明血管和 唾液酸转移酶ST 3Gal-I、ST 3Gal-IV和最近鉴定的ST 3Gal-VI的先天免疫功能。 它们在掩蔽特定的脱唾液酸糖蛋白受体配体中的作用，以及ST 3Gal-IV作为人VWD的修饰剂的可能参与将被探索。 我们对ST 3Gal唾液酸转移酶突变体的研究进一步导致了这样的假设，即ST 3Gal-VI将被发现对于选择素配体形成以及因此在炎症期间的先天免疫功能是必需的。该假设将通过产生ST 3Gal-VI基因功能缺陷的小鼠并使它们经受PPG核心设施的表型分析来研究，所述表型分析涉及确定血管和先天免疫参数以及选择素配体形成， 基于选择素的生理反应。还假设这些ST 3Gal唾液酸转移酶的血管和先天免疫功能影响伤口愈合和细菌入侵。将使用PPG核心机构研究ST 3Gal-I、ST 3Gal-IV和ST 3Gal-VI的这些推定保护作用。 这些研究将确定α 2 -3连接的唾液酸在调节血管和免疫系统中发挥作用的机制，并可能建立可能导致人类疾病新见解的重要作用。

Enzymes that transfer sialic acids to glycoproteins and glycolipids are termed sialyltransferases. Sialic acid addition generally terminates further oligosaccharide biosynthesis and thereby can generate as well as mask biologically relevant glycan structures. Among vertebrates, a highly conserved sialyltransferase gene family exists that contains at least eighteen members. These genes exhibit expression profiles that are commonly developmentally restricted and cell- or tissue-type specific. From limited studies thus far, sialic acid linkages have been found to regulate cell trafficking, adhesion, glycoprotein half-life in plasma, and signal transduction involving multi-subunit receptor complexes. In determining sialyltransferase gene function in vivo, mouse germline mutations are produced using Cre-loxP site-directed recombination in embryonic stem cells and adult mice. Subsequently, physiologic parameters are assessed by the use of specific phenotyping Core facilities provided by this Program Project Grant. In this manner, our previous findings have established critical hemostatic and immunologic roles for specific sialyltransferase genes. For example, ST3Gal-I and ST3Gal-IV promote platelet homeostasis, while ST3Gal-IV deficiency specifically results in an autosomal dominant yon Willebrand disease-like syndrome in mice. The goal of this project is to further elucidate the vascular and innate immune functions of sialyltransferases ST3Gal-I, ST3Gal-IV, and the recently identified ST3Gal-VI. Their roles in masking specific asialoglycoprotein receptor ligands, and the possible involvement of ST3Gal-IV as a modifier of human VWD will be explored. Our studies of ST3Gal sialyltransferase mutants have further resulted in the hypothesis that ST3Gal-VI will be found essential for selectin ligand formation and thus innate immune function during inflammation. This hypothesis will be investigated by generating mice deficient in ST3Gal-VI gene function and subjecting them to phenotypic analyses with PPG Core facilities, that involve determining vascular and innate immune parameters as well as selectin ligand formation and selectin-based physiologic responses. The vascular and innate immune functions of these ST3Gal sialyltransferases are also hypothesized to affect wound healing and bacterial invasion. These putative protective roles of ST3Gal-I, ST3Gal-IV and ST3Gal-VI will be investigated with the PPG Core facility. These studies will define the mechanisms by which alpha2-3 linked sialic acids function in modulating vascular and immune systems, and will likely establish important roles that may lead to new insights in human disease.