Glycome-Proteome Interactome Cartography via Proximity Tagging

Glycans are now recognized as essential biomolecules for life, and an increasing number of investigators and studies continue to reveal the myriad ways in which these post-translational modifications regulate important biological events. Chief among the ways in which glycans carry out their roles is by engaging in binding interactions with glycan-binding proteins (GBPs). Such interactions are important for proper physiology or in the activation of disease. Thus, achieving a precise molecular understanding of these interactions can pave new avenues for synthetic control and potentially therapeutic strategies to regulate disease. In this Account, we discuss our efforts toward revealing the collective interactions between glycans, protein glycoconjugates, and GBPs in cells, with an eye toward identifying the specific glycan-carrying proteins that interact with the GBPs in a functional manner.While the importance of studying glycan-GBP interactions has long been established, prior to our work, much of glycoscience had been occupied with the systematic assignment of the structural features of glycans required for recognition by GBPs in vitro, often using homogeneous glycan arrays. This important body of work enabled the preliminary identification of principal GBP-glycan binding preferences and allowed the rational design of functionalized glycan molecules to use as competitive inhibitors. Equipped with these two sets of important tools, expanding our understanding of glycan-GBP interactions from in vitro glycan binding preferences toward that of glycoprotein-GBP interactions in vivo has become timely and possible. We describe the conceptual motivation behind developing proximity tagging technologies to capture these glycoprotein-GBP interactions and how we used these interactome data sets to guide the discovery of functional interactors or create new hypotheses. Furthermore, we describe how proximity tagging can continuously be used toward application in our work, and the potential routes of investigation it may facilitate in the coming years.