Chemical Editing of Proteoglycan Architecture

Proteoglycans are heterogeneous macromolecular glycoconjugates that orchestrate many important cellular processes. While much attention has focused on the poly-sulfated glycosaminoglycan chains that decorate proteoglycans, other important elements of proteoglycan architecture, such as their core proteins and cell surface localization, have garnered less emphasis. Hence, comprehensive structure-function relationships that consider the replete proteoglycan architecture as glycoconjugates are limited. Here, we present a comprehensive approach to study proteoglycan structure and biology by fabricating defined semi-synthetic modular proteoglycans that can be tailored for cell surface display. To do so, we integrate amber codon reassignment in the expression of sequence-fined proteoglycan core proteins, metabolic oligosaccharide engineering to produce functionalizable glycosaminoglycans, and bioorthogonal click chemistry to covalently tether the two components. These materials permit the methodical dissection of the parameters required for optimal binding and function of various proteoglycan-binding proteins, and they can be modularly displayed on the surface of any living cell. We demonstrate that these sophisticated materials can recapitulate the functions of native proteoglycans in mouse embryonic stem cell differentiation and cancer cell spreading, while permitting the identification of the most important contributing elements of proteoglycan architecture toward function. This technology platform will confer structural resolution toward the investigation of proteoglycan structure-function relationships in cell biology.