Sialylation in the Maintenance and Metabolic Plasticity of Neural Stem Cell-Like Brain Tumor Cells

PROJECT SUMMARY/ABSTRACT One of the least-investigated areas of research in brain pathologies is glycosylation, which is a critical regulator of cell surface protein structure and function. ST6Gal1 is the primary enzyme that a2,6 sialylates N-glycosylated proteins destined for the plasma membrane or secretion. Sialylation adds a negatively-charged, sialic acid to the end of an oligosaccharide chain of a glycoprotein. Sialylation of distinct protein subsets has important effects on conformation, clustering and cell surface retention as has been found for some integrins, growth factor receptors and death receptors. Through this mechanism, ST6Gal1 regulates phenotypes including survival, invasion, and stem cell maintenance. However, there are critical gaps in our understanding of how ST6Gal1-mediated sialylation impacts brain tumor cell growth or differentiation state, and there are no studies identifying a2,6 sialylated proteins or ST6Gal1 regulated pathways in brain tumors. Our preliminary data demonstrate a novel, pro-tumorigenic role for a2,6 sialylation and ST6Gal1 in the deadly brain tumor glioblastoma. We seek to determine whether ST6Gal1- mediated a2,6 sialylation promotes brain tumor initiating cell maintenance and metabolic plasticity. In the short- term, our results will lead to an improved understanding of how ST6Gal1-mediated a2,6 sialylation regulates protein expression and function to impact brain tumor propagation. In the long-term, these studies may offer the potential for new mechanisms of therapeutic intervention for the treatment of brain tumors as ST6Gal1 inhibitors are under development.