Effects of T217 Phosphorylation on Tau Localization and Microtubule Binding

Background Biomarker-based early detection of Alzheimer’s disease (AD) is necessary for developing therapies that counter AD symptom onset. Promising biomarkers include tau phosphorylated at T181, T217 or T231, levels which can be measured in cerebrospinal fluid plasma. Little known about functional consequences phosphorylation these sites, though, especially taupT217. We thus sought to identify where taupT217 localized the brains human patients and model mice, cultured mouse neurons, and, a more context, determine if affects binding microtubules. Method Brain tissue from neurons were analyzed by western blotting immunofluorescence microscopy compare intracellular localization taupT217, taupT181, taupT231 (AT180 epitope) taupS396,pS404 (PHF1 epitope). EGFP-tau (2N4R) was expressed CV-1 African green monkey kidney fibroblasts as wild type (WT), T217A non-phosphorylatable, T217E pseudo-phosphorylated versions fluorescent fusion protein. Fluorescence recovery after photobleaching (FRAP) used assay turnover rates proteins on microtubules, surrogate measurement affinity. Result In abundant somatodendritic compartment co-localized with neurofibrillary tangles. concentrated puncta closely associated dendritic spines. Both vivo only partially taupT181 taupT231. Exposure extracellular oligomers tau, but not amyloid-β, increased cells, EGFP-tauT217E recovered faster than EGFP-tauT217A EGFP-tauT217. Conclusion Intracellular enriched locations normally lack much oligomers. TaupT217 near spines, suggesting possible role altering synaptic activity. The fluorescence compared EGFP-tauT217 implies reduces tau’s affinity