Pyroglutamate modification of a-synuclein in human synucleinopathies

• Applicant: Professor Dr. Steffen Roßner
• Subject Area: Molecular and Cellular Neurology and Neuropathology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547786666

Human synucleinopathies are a heterogenic class of neurodegenerative disorders characterized by aggregation of the protein alpha-synuclein (aSyn). They include Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). PD, DLB and MSA display specific characteristics regarding their cell type- and brain region-specific aSyn deposition. Furthermore, a panel of post-translational protein modifications has been identified that affects aSyn structure and aggregation and, thereby, contributes to disease initiation and/or progression. We recently discovered a novel pyroglutamate (pE) modification of N-terminally truncated aSyn that is associated with neurotoxic oligomer formation and might be catalyzed by glutaminyl cyclase (QC) or its isoenzyme isoQC. In the present proposal we will test the hypothesis that defined pE-modified aSyn variants – pE24-aSyn, pE62-aSyn and pE79-aSyn – display specific characteristics regarding the cell type- and brain region-specific aSyn aggregation in the clinical entities investigated. The proposed experimental work will be done using well-characterized human brain tissue and immunohistological methods as well as biochemical extraction procedures to detect different aggregation forms of pE-aSyn such as oligomers and fibrils in tissue fractions characterized by different solubility in detergents. To test this hypothesis, we will address three specific aims. Aim 1: Are there brain region-specific characteristics in the abundance of the pE-aSyn variants? If so; do they follow a similar pattern in the three synucleinopathies investigated? Aim 2: Is the cell type-specific localization of the different pE-aSyn variants similar? Are the pE-aSyn variants co-localized to QC or isoQC? Are there differences in the cell type-specific localization of pE-aSyn variants in PD, DLB and MSA? Aim 3: Can pE-aSyn variants be detected in oligomeric and fibrillary aggregates isolated from human brain tissue? What is the proportion of distinct pE-aSyn variants in aggregates characterized by solubility in detergents? Do pE-aSyn variants trigger aSyn aggregation in seed amplification assays? The results of this study will allow drawing conclusions on the implications of pE24-aSyn, pE62-aSyn and pE79-aSyn in human synucleinopathies.

• DFG Programme: Research Grants