Grant: Discovery Grants Program - Individual

The post-translational modification of proteins is essential to the function of these biomolecules and often serves as a critical biochemical regulatory mechanism. Over half of all proteins in human cells are glycosylated, making glycosylation (glycans) the most abundant post-translational modification. In humans, most extracellular and cell-surface glycans contain terminal sialic acid (also called neuraminic acid) residues. These sialosides, by virtue of their location at the periphery of extracellular glycans, are often the first point of interaction in cell-cell and cell-pathogen interactions. Thus, sialosides are often critical to infection, development, and immunity. For example, sialosides are used by viruses to distinguish appropriate host cells for infection and by our own immune system to recognize self from non-self. We propose to expand our research program in the chemical biology of sialosides to develop new research tools to understand the role of sialosides, and enzymes that modify them, in cell biology. As part of our program we will identify new competitive inhibitors with selectivity for bacterial neuraminidase enzymes (NEU, also known as sialidases) of S. pneumoniae. These inhibitors will be valuable new tools for studying the role of bacterial NEU in infection. A major component of our program will be the development of new bioconjugate strategies to generate defined polysialic acid (PSA) glycoconjugates and tools to study their metabolism by cells. These tools will help us to understand the processing of PSA glycoproteins and could provide new tools for improving therapeutic proteins. We will also study enzymes involved in the biosynthesis of sialosides - in particular, we will examine the specific role of the N-acylneuraminate-9-phosphatase (NANP) that has previously been thought to be essential to sialoside biosynthesis. Based on recent findings, we propose to generate chemical tools to identify alternative phosphatases that bypass NANP in vivo, as well as specific covalent and competitive inhibitors of this enzyme. These tools will be essential to understanding the fundamental mechanisms of sialic acid biosynthesis in human cells. Together these projects will form a broad program in the chemical biology of sialosides and will provide excellent training in carbohydrate chemistry, bioorganic chemistry, medicinal chemistry, bioconjugate chemistry, enzymology, biochemistry, and molecular biology.