Monosialoganglioside GM1 Deficiency Inhibits the Neurotrophic Effects of GDNF by Disrupting Lipid Raft Assembly

Abstract

Recent studies have shown that monosialoganglioside GM1 deficiency can inhibit the signal transduction process of glial cell line-derived neurotrophic factor (GDNF), which plays an important role in the pathogenesis of Parkinson's disease (PD). However, its specific mechanism still needs to be explored. We inhibited the expression of GM1 by treating cells with D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP). CCK-8 assay, EdU cell proliferation assay and Western blot assay were used to evaluate the effect of GM1 deficiency on the proliferation and differentiation of SH-SY5Y cells induced by GDNF and on the GDNF-RET signaling pathway. Lipid rafts were isolated by Triton X-100 solubilization and OptiPrepTM density gradient centrifugation. The alterations of lipid raft assembly and the translocation of RET into lipid rafts were evaluated after PDMP treatment. We found that PDMP treatment inhibited the proliferation and differentiation of SH-SY5Y cells induced by GDNF and reduced the phosphorylation of RET and its downstream signaling molecules Erk and Akt. In addition, after PDMP treatment, caveolin-1 and flotillin-1, the prototypical markers of lipid rafts, diffused from lipid rafts to non-lipid raft microdomains, and GDNF-induced RET translocation into lipid rafts was also reduced. These alterations could be partially reversed by adding exogenous GM1. Our results suggest that ganglioside GM1 deficiency could compromise the neurotrophic effects and signals downstream of GDNF by altering the assembly of lipid raft membrane microdomains.