Acidic oligosaccharide sugar chain, a marine-derived oligosaccharide, activates human glial cell line-derived neurotrophic factor signaling.

Gial derived neurotrophic factor (GDNF) modulates neuronal cell differentiation during development and protects against neurodegeneration by preventing apoptosis at maturity. GDNF's role in tissue maintenance has generated interest in the therapeutic potential of GDNF in treating neurological disorders such as Parkinson's disease. Heparan sulfate has been shown to be essential for GDNF signaling and altering the levels of heparan sulfate promotes or inhibits GDNF functional activity. To search for other oligosaccharides capable of modulating GDNF activity as potential therapeutic molecules, we investigated the effect of acidic oligosaccharide sugar chain (AOSC) and its sulfated derivative on GDNF induced neurotrophic events by using Western-blotting, immunofluorescence cell staining, and immunoprecipitation techniques in PC12 cells expressing the GDNF receptors GFR alpha 1-Ret. AOSC significantly improved the neurite outgrowth and activated c-Ret phosphorylation in PC12-GFR alpha 1-Ret cells, but its sulfated derivative inhibited GDNF activity. Studies to understand the opposing biological effects of AOSC and its sulfated derivative on GDNF activity demonstrated that reduced GDNF binding to PC12-GFR alpha 1-Ret cell surface in the presence of the sulfated derivative likely suppressed GDNF activity as both AOSC and its sulfated derivatives had similar binding affinities to GDNF. This study illustrates the importance of oligosaccharide structure and charge on influencing GDNF activity and the potential use of oligosaccharides in modulating GDNF activity for therapeutic purposes.