Post-translational modifications (PTMs) of the axonal microtubule-associated protein tau have been implicated in the development of tauopathies, a group of diseases characterized by the formation of pathological tau aggregates, including Alzheimer's disease (AD). Among the PTMs, hyperphosphorylation is of particular importance, characterized by an abnormal increase in phosphorylation at specific sites. However, the downstream pathological consequences of tau hyperphosphorylation remain unclear. In this study, we investigated the effects of pseudohyperphosphorylated tau (PHP-Tau) in model neurons, mimicking a disease-like hyperphosphorylation of tau at specific residues. We used a multi-omics approach, including proteomics, phosphoproteomics and lipidomics, to analyze molecular changes associated with tau hyperphosphorylation. In parallel, 3D reconstruction of super-resolution microscopy images was used to assess changes in axonal microtubule organization. Our integrative analysis reveals that tau hyperphosphorylation is associated with alterations across multiple molecular layers and impacts cytoskeletal organization. Notably, changes were observed in STMN1, a protein involved in microtubule assembly and disassembly, and in GM3, a sphingolipid associated with AD. Furthermore, multi-omics data indicate that tau hyperphosphorylation affects pathways associated with AD and is linked to structural alterations in microtubule organization. These findings provide new insights into how pathological tau may contribute to neuronal dysfunction by coupling molecular dysregulation with structural changes in microtubule architecture.

Co-authors: Nataliya Trushina, Sai Sanwid Pradhan, Jeelka Hessenius, Venketesh Sivaramakrishnan, Roland Brandt