Decoding the Structure-Function Relationships of Glycosaminoglycans in the Lung using Heparan Sulfate Libraries - Project Summary Heparan sulfate glycosaminoglycans (HS GAGs) are highly sulfated polysaccharides that regulate many important pulmonary processes, including development, homeostasis, structural support, and inflammation, as well as human diseases such as pulmonary hypertension, chronic obstructive pulmonary disease, pulmonary fibrosis, and asthma. The structural complexity of HS endows it with the ability to regulate these biological processes, but also severely hinders the production of defined HS oligosaccharides. As such, efforts to elucidate the HS sequence `code' have been stymied by a lack of chemical, analytical and computational tools to decipher the biological functions of HS. Thus, the objectives of the proposed research are to: (1) advance synthetic methods and access to comprehensive libraries of structurally-defined HS oligosaccharides; (2) decipher how HS-binding proteins `read' and sulfotransferases `write' the sulfation code; (3) investigate the functional roles of HS structures in pulmonary function and disease, with a focus on targeting HS- binding proteins to modulate pathological processes in the lung. Recently, we developed new, streamlined synthetic strategies that significantly expedite HS synthesis, enabling access to comprehensive, structurally defined libraries of HS tetrasaccharides. Notably, this was achieved in part via the use of automated synthesis, demonstrating the power of our synthetic methods, and proving the feasibility of expanding upon our solution-phase automation platform to accelerate access to large libraries of HS GAGs. Our library enabled systematic investigations that were not previously possible into the HS sequence dependence of several fibroblast growth factor (FGF) and chemokine family members. This work further necessitated the development of new computational, machine learning-based methods to analyze the binding datasets that were produced and visualize the unique sequence preferences or `fingerprints' of each protein. These results combined provided compelling new evidence that the complex structure of HS encodes key biological information that is `read' by interacting proteins. In this grant, we will build on these exciting discoveries, methods, and frameworks. First, we will create expanded libraries of HS oligosaccharides to access new regions of the HS sequence landscape (Aim 1). We will also further develop our promising solution-phase automation platform to significantly enhance access to these libraries (Aim 2). Our HS libraries, both current and proposed, will be used to study the molecular recognition of HS by `readers' (e.g. FGFs and chemokines) and `writers' (e.g. sulfotransferases) and exploit their interactions in pulmonary diseases (Aims 3a, 3b, and 4). Moreover, we will continue developing new computational methods to decipher how the sulfation code is `read' (Aim 3c). Together, these studies will further a fundamental understanding of the structure-function relationships of HS and provide novel strategies for understanding, targeting, and treating diseases in the lung.
