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 -acetyl-glucosamine (O-GlcNAc) in vivo . One of these proteins, α-synuclein, is a toxic aggregating protein associated with synucleinopathies, including Parkinson's disease. However, the effect of O-GlcNAcylation on α-synuclein is not clear. Here, we use synthetic protein chemistry to generate both unmodified α-synuclein and α-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 α-synuclein aggregation, while not affecting the membrane binding or bending properties of α-synuclein. O-GlcNAcylation is also shown to affect the phosphorylation of α-synuclein in vitro and block the toxicity of α-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. O-linked N -acetyl-glucosamine (O-GlcNAc) has been identified as an endogenous modification of α-synuclein; however, its effect on the properties of the protein is unclear. Now, recombinant protein and synthetic peptides have been combined to produce both unmodified and site-specifically O-GlcNAc-modified α-synuclein. The O-GlcNAc modification at threonine 72 was shown to inhibit the aggregation and associated toxicity of α-synuclein.