Phosphatase treatment dephosphorylated tau in rTg4510 brain extract (Fig. 7d) without changing HMW tau levels (Fig. 7e), resulting in a significant reduction of cellular uptake of tau (Fig. 7f).
Importantly, neuronal uptake of HMW tau occurred in vivo as well; human tau uptake in neurons was detected in young rTg4510 (pre-tangle stage) (Fig. 1j–l) and WT (Supplementary Fig. 6) mice injected with the HMW SEC fraction of Tg4510 (12 months) brain extract, but not in those injected with the LMW fractions.
There was no difference in cell viability between tau-aggregate positive and negative cells for up to 4 days (Supplementary Fig. 10).
The PBS- extractable tau species from rTg4510 brain had higher levels of phosphorylation compared with the tau species obtained from rTg21221, especially those associated with some specific phosphorylation sites such as pT205, pS262, pS400, pS404, pS409 and pS422.
SEC analysis of the molecular weight distribution of tau demonstrated that rTg21221 brain extracts (PBS-soluble, 3,000g) contained primarily LMW species and very low levels of HMW tau species, whereas rTg4510 brain extract showed both HMW and LMW peaks (Fig. 2e,f).
The HMW tau species from the AD brain were highly phosphorylated compared with those from control brain (Fig. 6m).
However, the AD brain extract (3,000g) contained significantly higher levels of phosphorylated tau (Fig. 6h,i,m) when compared with the control brain, especially those associated with some specific phosphorylation sites such as pS199, pS396 and pS404 (Fig. 6i).
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If you find BEL Commons useful in your work, please consider citing: Hoyt, C. T., Domingo-Fernández, D., & Hofmann-Apitius, M. (2018). BEL Commons: an environment for exploration and analysis of networks encoded in Biological Expression Language. Database, 2018(3), 1–11.