O-GlcNAc modification blocks the aggregation and toxicity of the protein α-synuclein associated with Parkinson's disease

Several aggregation-prone proteins associated with neurodegenerative diseases can be modified by O-linked N-acetylglucosamine (O-GlcNAc) in vivo. One of these proteins, alpha-synuclein, is a toxic aggregating protein associated with synucleinopathies, including Parkinson's disease. However, the effect of O-GlcNAcylation on alpha-synuclein is not clear. Here, we use synthetic protein chemistry to generate both unmodified alpha-synuclein and alpha-synuclein bearing a site- specific O-GlcNAc modification at the physiologically relevant threonine residue 72. We show that this single modification has a notable and substoichiometric inhibitory effect on alpha-synuclein aggregation, while not affecting the membrane binding or bending properties of alpha-synuclein. O-GlcNAcylation is also shown to affect the phosphorylation of alpha-synuclein in vitro and block the toxicity of alpha-synuclein that was exogenously added to cells in culture. These results suggest that increasing O-GlcNAcylation may slow the progression of synucleinopathies and further support a general function for O-GlcNAc in preventing protein aggregation.