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Small molecule Interactions with Heparan sulfate


Heparan sulfate (HS) has been shown to be involved in a variety of mechanisms indispensable for normal development and physiological functions, as well as pathophysiological processes such as cancer. Small molecule antagonists of HS -protein interactions could provide novel approaches to inhibiting a variety of disease processes. In a search for small molecule antagonists of HS we examined the activity of bis-2-methyl-4-amino-quinolyl-6-carbamide (surfen). Fluorescence-based titrations indicate that surfen binds to glycosaminoglycans, neutralizes the anticoagulant activity of both unfractionated and low molecular weight heparins and inhibits enzymatic sulfation and degradation reactions in vitro. Addition of surfen to cultured cells blocks FGF2-binding and signaling dependent on cell surface HS, and prevents both FGF2 and VEGF165-mediated sprouting of endothelial cells in Matrigel. Surfen also blocks HS mediated cell adhesion to the Hep-II domain of fibronectin and prevents infection by Herpes simplex virus -1 dependent on glycoprotein D interaction with HS. These findings demonstrate the feasibility of identifying small molecule antagonists of HS and raise the possibility of developing pharmacological agents to treat disorders that involve glycosaminoglycan-protein interactions. Facilitating the uptake of molecules into living cells is of substantial interest for basic research and drug delivery. We show that a derivative of neomycin, guanidinoneomycin (GNeo), can deliver large bioactive molecules, and its uptake depends entirely on cell surface HS. The high selectivity of guanidinoneomycin for HS suggests the possibility of exploiting differences in proteoglycan compositions to target delivery to different cell types. Saporin-GNeo conjugates were used to test the possibility of differentially targeting cancer cells. To explore the utility of these molecules in therapeutic applications other than toxin delivery, we demonstrated that GNeo can be utilized to correct enzyme defects in lysosomal storage diseases, specifically mucopolysaccharidosis VII. The work presented in this dissertation represents the first characterization of the biological utility and therapeutic applicability of small molecules that interact with HS, and supports future development of more potent and selective derivatives

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