O-GlcNAcylation effect on Tau in modulating its seeding and cellular transmission in Alzheimer's Disease

Post-translational modifications critically regulate neurodegenerative disease progression. In Alzheimers disease (AD) and tauopathies, Tau hyperphosphorylation promotes aggregation and pathological spreading, whereas O-GlcNAcylation has emerged as a protective modification alongside its interplay with phosphorylation. However, the role of in vitro site-specific and global O-GlcNAcylation in Tau proteinopathy remains elusive. Here, using full-length Tau-441 (2N4R), we showed that O-GlcNAcylated Tau aggregated slowly, formed distinct aggregate morphology and exhibited reduced seeding capacity compared to wild-type (WT) Tau. Under phase-separated conditions, O-GlcNAcylated Tau formed oligomer like condensates. Mutation of the key O-GlcNAc sites reduced O-GlcNAc-transferase (OGT) mediated O-GlcNAcylation, cellular transmission and affected cross-talk with phosphorylation relative to WT. OGT overexpression alleviated WT-Tau toxicity in cells, and O-Tau fibrils were less toxic to primary cortical neurons compared to WT Tau fibrils. Finally, an in-house novel site-specific S422 O-GlcNAc-Tau antibody revealed reduced S422 O-GlcNAcylation in AD brain tissues, highlighting its protective role in AD pathogenesis.