Glycation Produces Topologically Different α-Synuclein Oligomeric Strains and Modulates Microglia Response via the...

α-Synuclein, a key player in Parkinson's disease and other synucleinopathies, possesses an inherently disordered structure that allows for versatile structural changes during aggregation. Microglia, the brain immune cells, respond differently to various α-synuclein strains, influencing their activation and release of harmful molecules, leading to neuronal death. Post-translational modifications, such as glycation in α-synuclein, add a layer of complexity to microglial activation. This study aimed to explore the impact of glycation on α-synuclein aggregation and microglial responses, which have not been studied before. Biophysical analyses revealed that glycated α-synuclein oligomers had distinct morphologies with a more negative and hydrophobic surface, preventing fibril formation and interfering with membrane interactions. Notably, there was increased cytosolic Ca²⁺ dysregulation, redox stress, and mitochondrial instability compared to cells exposed to unmodified α-synuclein oligomers. Additionally, glycated α-synuclein oligomers exhibited impaired binding to Toll-like receptor 2, compromising downstream signaling. Surprisingly, these oligomers promoted TLR4 endocytosis and degradation. In our experiments with oligomers, glycated α-synuclein oligomers preferred NLRP3 inflammasome-mediated neuroinflammation, contributing differently from unmodified α-synuclein oligomers. In summary, this study unveils the mechanism underlying the effect of glycation on α-synuclein oligomers and highlights the conformation-specific microglial responses toward extracellular α-synuclein.