Proteome-based investigation of O-GlcNAcylation in a C. elegans model of Ageing and Alzheimer's disease: Functional Support for Earlier Hypothesis-Generating Findings

The monosaccharide N-acetyl-glucosamine (GlcNAc), which dynamically modifies serine and threonine residues of nuclear and cytoplasmic proteins, is a key regulator of numerous biological processes. Investigating O–GlcNAc modification in vivo and in vitro remains challenging, making animal models essential for gaining powerful insights into this post-translational modification. In this study, we conducted a proteomic analysis for identifying O–GlcNAc–modified proteins in both early and adult larval stages of N2 wild-type Caenorhabditis elegans and in aex–3p::tau(V337M), a nematode model of ageing and Alzheimer′s disease using a high–resolution nano–LC–ESI mass spectrometry approach. We found that O–GlcNAcylation in C. elegans is developmentally regulated and is disrupted in a tauopathy model. Wild–type worms transition from RNA processing in larvae to broader regulation of RNA metabolism and protein stability, whereas tau-expressing worms display stress– and signalling–related features. O-GlcNAcylated PDI–2 emerges as a candidate regulator of protein quality control and decrease of O–GlcNAc levels suggests competition with hyperphosphorylated tau. These findings position O–GlcNAcylation as a context–dependent modulator of proteostasis with therapeutic relevance for tauopathy.