Temporal Trajectories of the Tau Aggregate Interactome Reveal Stage‐Specific Vulnerabilities in Alzheimer's Disease

Tau aggregation is a central pathological feature of Alzheimer's disease, yet how different forms of tau-ranging from monomers to small soluble aggregates and mature fibrils-interact with the cellular environment remains poorly understood. Here, we combine immunoaffinity proteomics with single-molecule techniques and super-resolution microscopy to systematically map the tau interactome across defined aggregation states, spanning monomeric tau, nanoscopic soluble aggregates, and fibrillar species. Using post-mortem Alzheimer's disease brain tissue, we identify distinct functional modules associated with different aggregation states: while proteostasis factors and immune-related proteins preferentially associate with nanoscopic aggregates (oligomers), cytoskeletal, metabolic, and RNA-binding proteins are enriched for mature fibrillar tau. Single-molecule microscopy directly confirms this conformation-dependent recruitment for key interactors including Hsp70-2, ENO1, hnRNPA1, APP, EAAT4, and ubiquitin. A primary-neuron system with accelerated tau aggregation is used to model these findings in a controlled system, showing striking similarities to the brain samples. Finally, pseudotime analysis reconstructs a progressive remodelling of the tau interactome across disease progression, revealing stage-specific pathway vulnerabilities. Together, these results establish a temporally resolved framework for tau pathology shaped by protein interactions and identify potential therapeutic intervention points for investigation across stages of disease.