With this Award, the Chemistry of Life Processes Program is supporting Professor Matthew Pratt of the University of Southern California to develop chemical biological tools to study protein glycosylation and its impact on function, with a particular focus on modifications of the O-GlcNAc (O-linked N-acetylglucosamine) variety. Many proteins are modified after they are made by the addition of carbohydrates in a process termed glycosylation. Decades of research showed that protein glycosylation plays key roles in cell biology, including cell-cell connections and signaling between cells. However, the traditional biological approaches that were used to make these discoveries have critical limitations that prevent their application towards gaining a detailed understanding of these important associations. To overcome these roadblocks, the Pratt lab seeks to develope and test chemical tools that will enable the selective visualization, identification, and characterization of protein glycosylation. These tools will be applied to the investigation of the biochemistry of glycosylation and are to made available to other laboratories, as well. Additionally, we are also applying one of these chemical tools to investigate the role of a specific type of glycosylation, termed O-GlcNAcylation, in the death of cells. There is an important element of undergraduate research in the chemical and biological sciences in this project, and outreach to those in inner city schools with an eye toward increasing the participation or members of traditionally underrepresented groups in STEM studies.
Metabolic chemical reporters of protein glycosylation are analogues of monosaccharides that bear bioorthogonal reactive groups, such as azides or alkynes. If these analogues are similar enough to their natural counterparts, so as to not interfere with the chemistry of native glycosidation enzymes, they will be metabolized by cells and incorporated into glycans. The azides or alkynes can then undergo selective reactions, such as the copper(I)-catalyzed azide-alkyne cycloaddition, to install visualization or identification tags. Unfortunately, this research group and others have shown that the majority of previously developed reporters are not selective for one type of glycosylation, limiting their use in biological discovery. Recently, the first reporter that is specific for one type of glycosylation, namely O-GlcNAc modifications, was developed in these laboratories. This project is designed to build upon this exciting result in two ways. First, the Pratt lab will create and characterize other reporters with the goal of identifying chemical tools that are selective for other types of glycosylation. Second, they will use their selective O-GlcNAc reporter to investigate the role of O-GlcNAcylation on cell-death proteins, which are key to the fundamental biology of all metazoans.
