Trehalose enhances the degradation of Tau through the autophagy pathway

Abstract

Modulating the Tau level may represent a therapeutic target for Alzheimer Disease, as accumulating evidence shows that Abeta-induced neurodegeneration is mediated by Tau. It is therefore important to understand the expression and degradation of Tau in neurons. Recently we showed that over expressed mutant Tau and Tau aggregates are degraded via the autophagic pathway in an N2a cell model, and how autophagy contributes to Tau cleavage, aggregation, and degradation (Wang et al., HMG2009). Here we investigated how different aspects of autophagy contribute to the degradation of Tau in cultured primary neurons. We further examined whether the stimulation of autophagy can reduce aggregation and alleviate cytotoxicity in a regulable N2a cell model of Tauopathy. Autophagy was induced by Trehalose in Neuroblastoma cells and rat primary neurons. The activation of autophagy was validated by Flux assays and fluorescence microscopy. Tau level was analysed by western blot with a pan-Tau antibody and a series of phosphorylation dependent antibodies: 12E8, PHF1, AT8 and AT180.Tau aggregates were separated with Sarkosyl extraction and visualized with Thioflavin S staining. Trehalose activated autophagy in rat cortical neurons, as seen by (1) elevated LC3-II levels, (2) an increased number of autophagosomes, (3) stimulated flux and (4) reduced p62 level, a known substrate of autophagy. At the same time Trehalose significantly reduced the endogenous Tau level. Phosphorylation seems to have no effect on Tau degradation by autophagy, as Tau phosphorylated at 12E8, PHF1, AT8 and AT180 sites was also decreased upon Trehalose treatment. In a N2a cell model of Tauopathy, Trehalose induced autophagy, which caused the reduction of Tau aggregation and toxicity. The activation of autophagy reduced endogenous Tau regardless of phosphorylation in primary cortical neurons and Tau aggregates in a N2a cell model of Tauopathy, indicating that stimulation of autophagy could serve as a therapeutic target.