α-Synuclein O-GlcNAcylation alters aggregation and toxicity, revealing certain residues as potential inhibitors of Parkinson’s disease

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 5; pp. 1511 - 1519
• Main Authors: Levine, Paul M., Galesic, Ana, Balana, Aaron T., Mahul-Mellier, Anne-Laure, Navarro, Mariana X., De Leon, Cesar A., Lashuel, Hilal A., Pratt, Matthew R.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29.01.2019
• Series: PNAS Plus
• Subjects: Acetylglucosamine - metabolism; Acylation - physiology; Agglomeration; Aggregates; alpha-Synuclein - metabolism; Animal models; Animals; Biocompatibility; Biological Sciences; Cell culture; Cells, Cultured; Chemical synthesis; Experiments; Female; Fibers; Human tissues; Mice; Mice, Inbred C57BL; Neurodegeneration; Neurodegenerative diseases; Neurological diseases; O-GlcNAcylation; Organic chemistry; Parkinson Disease - metabolism; Parkinson Disease - pathology; Physical Sciences; PNAS Plus; Pregnancy; Protein Aggregation, Pathological - pathology; Protein interaction; Protein Processing, Post-Translational - physiology; Proteins; Proteomics; Synuclein; Therapeutic applications; Toxicity; synuclein; aggregation; amyloid; O-GlcNAc; Parkinson’s disease
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1808845116

A compelling link is emerging between the posttranslational modification O-GlcNAc and protein aggregation. A prime example is α-synuclein, which forms toxic aggregates that are associated with neurodegeneration in Parkinson’s and related diseases. α-Synuclein has been shown to be O-GlcNAcylated at nine different positions in in vivo proteomics experiments from mouse and human tissues. This raises the possibility that O-GlcNAc may alter the aggregation of this protein and could be both an important biological mediator of neurodegeneration and also a therapeutic target. Here, we expand upon our previous research in this area through the chemical synthesis of six site-specifically O-GlcNAcylated variants of α-synuclein. We then use a variety of biochemical experiments to show that O-GlcNAc in general inhibits the aggregation of α-synuclein but can also alter the structure of α-synuclein aggregates in site-specific ways. Additionally, an α-synuclein protein bearing three O-GlcNAc modifications can inhibit the aggregation of unmodified protein. Primary cell culture experiments also show that several of the O-GlcNAc sites inhibit the toxicity of extracellular α-synuclein fibers that are likely culprits in the spread of Parkinson’s disease. We also demonstrate that O-GlcNAcylation can inhibit the aggregation of an aggressive mutant of α-synuclein, indicating that therapies currently in development that increase this modification might be applied in animal models that rely on this mutant. Finally, we also show that the pan-selective antibody for O-GlcNAc does not generally recognize this modification on α-synuclein, potentially explaining why it remains understudied. These results support further development of O-GlcNAcylation tools and therapeutic strategies in neurodegenerative diseases.