O-GlcNAc modification forces the formation of an α-Synuclein amyloid-strain with notably diminished seeding activity and pathology

Abstract

The process of amyloid fibril formation remains one of the primary targets for developing diagnostics and treatments for several neurodegenerative diseases (NDDs). Amyloid-forming proteins such α-Synuclein and Tau, which are implicated in the pathogenesis of Alzheimer's and Parkinson's disease, can form different types of fibril structure, or strains, that exhibit distinct structures, toxic properties, seeding activities, and pathology spreading patterns in the brain. Therefore, understanding the molecular and structural determinants contributing to the formation of different amyloid strains or their distinct features could open new avenues for developing disease-specific diagnostics and therapies. In this work, we report that O-GlcNAc modification of α-Synuclein monomers results in the formation of amyloid fibril with distinct core structure, as revealed by Cryo-EM, and diminished seeding activity in seeding-based neuronal and rodent models of Parkinson's disease. Although the mechanisms underpinning the seeding neutralization activity of the O-GlcNAc modified fibrils remain unclear, our in vitro mechanistic studies indicate that heat shock proteins interactions with O-GlcNAc fibril inhibit their seeding activity, suggesting that the O-GlcNAc modification may alter the interactome of the α-Synuclein fibrils in ways that lead to reduce seeding activity in vivo. Our results show that post-translational modifications, such as O-GlcNAc modification, of α-Synuclein are key determinants of α-Synuclein amyloid strains and pathogenicity. These findings have significant implications for how we investigate and target amyloids in the brain and could possibly explain the lack of correlation between amyloid burden and neurodegeneration or cognitive decline in some subtypes of NDDs.

Development and validation of an expanded antibody toolset that captures alpha-synuclein pathological diversity in Lewy body diseases

“…By re-examining aSyn pathology using our antibody toolbox, we can conclusively determine whether LBs or other forms of aSyn pathology are genuinely absent in these cases. In addition, recent findings from our group indicate that certain PTMs, such as O-linked-Nacetylglucosaminylation (O-GlcNAcylation) and nitration, reduce the seeding activity of aSyn fibrils in primary cultures and in vivo models 140,141 . This suggests that the patterns of PTMs, rather than just the presence of aSyn aggregates, may play a crucial role in determining some of the pathogenic properties of aSyn.…”

Engineered reactivity of a bacterial E1-like enzyme enables ATP-driven modification of protein C termini

“…Advances in our ability to construct modified proteins have expanded the frontiers of our understanding of how post-translational modifications regulate transcription 61 , transduce cellular signals 62,63 , and go awry in neurodegenerative disease [64][65][66] ; and have propeled our ability to probe biochemical and biophysical function through the installation of chemical probes and payloads that cannot be genetically encoded 8,67,68 . The MccB/TeCH-tag system provides a new method for C-terminal protein activation that vastly expands the toolkit for protein semisynthesis and protein bioconjugation.…”

Brain-derived and in vitro-seeded alpha-synuclein fibrils exhibit distinct biophysical profiles

“…The commonality of a particular structure in a fibrillar mixture may not be a determinant of a dominant seeding fibril. Other factors might contribute, such as metal ions ( Uversky et al, 2001 ) and post-translational modifications (PTMs), which also affect seeding efficiency ( Balana et al, 2023 ). Also, our PIPES-based SAA reaction buffer with 150 mM NaCl is likely to have influenced the SAA fibril structure.…”