Development of Chemical Tools to Discover and Characterize Sialic Acid Mediated Interactions
Parker, Randy B.
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Glycosylation refers to the addition of carbohydrates onto proteins, lipids, and other biomolecules. Proteins and lipids on the cell surface are frequently found to be glycosylated. This glycosylation can have a number of functions, one of which is to mediate specific binding interactions between the glycans of glycoconjugates and glycan binding proteins. Such glycan-mediated interactions are implicated in numerous cell-signaling processes. Many of these glycan-mediated interactions involve a class of carbohydrates known as sialic acids. The presence of sialic acid on a glycan can recruit specific sialic acid binding partners. Alternatively, sialic acids can mask underlying glycan epitopes, thereby preventing protein binding. There are several challenges in studying sialic acid mediated interactions. Chapter 1 describes the importance of sialic acids as well as the challenges in studying their interactions. Sialidases are enzymes that hydrolytically cleave sialic acid from its underlying glycan. In this regard, sialidases have the potential to impact numerous cellular processes in a dynamic fashion. Relatively little is known about the substrates of mammalian sialidases. Chapter 2 describes a novel assay that takes advantage of chemical labeling of sialic acids to characterize sialidase substrate specificity towards various complex glycans. Chapter 3 focuses on efforts to develop assays to identify the protein components of sialidase substrates in a cellular context. Finally, Chapter 4 describes the development of a series of probes to discover novel sialic acid mediated interactions. Taken together, this work describes several new techniques that will allow for better understanding of sialic acid mediated interactions.