Discovery and Development of Small-Molecule Modulators for the Sulfation of Glycosaminoglycans and Studying the Role of O-GlcNAc on CREB through Semisynthesis

Citation

Cheung, Sheldon Ting Fong (2017) Discovery and Development of Small-Molecule Modulators for the Sulfation of Glycosaminoglycans and Studying the Role of O-GlcNAc on CREB through Semisynthesis. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9PR7T0K. https://resolver.caltech.edu/CaltechTHESIS:10032016-103410952

Abstract

Glycosaminoglycans (GAGs) are sulfated polysaccharides that play key roles in many cellular processes, ranging from viral invasion and cancer metastasis to neuronal development. Their diverse biological activities stem from their complex sulfation patterns, which are tightly regulated in vivo. For instance, the GAG chondroitin sulfate (CS) has been shown to undergo regiochemical sulfation during development and after spinal cord injury. However, few tools exist to modulate specific GAG sulfation patterns and study their importance in different biological contexts. Here, we identified the first cell-permeable small molecule that can selectively inhibit GAG sulfotransferases and modify the fine structure of GAGs. We demonstrate that the inhibitor reduces GAG sulfation in vitro and in cells and reverses CS-E-mediated inhibition of neuronal outgrowth. This small molecule may serve as a useful lead compound or chemical tool for studying the importance of CS and other GAGs in normal biology and disease.

The β-N-acetyl-D-glucosamine (O-GlcNAc) post-translational modification plays a major role in many diseases such as cancer, diabetes, and neurodegenerative disorders, but much is still unknown about its molecular-level influence on protein structure and function. Although post-translational modifications have been known to induce important structural changes in proteins, notably, no structures of O-GlcNAcylated proteins exist. The challenge of obtaining homogeneous glycoproteins bearing the GlcNAc sugar at defined sites has hindered the structural and biochemical studies of this modification. Here we have utilized a semisynthetic approach to generate a homogeneously O-GlcNAcylated form of cyclic-AMP response element binding protein (CREB) for structural and functional studies.

Thesis Files