Endogenous overproduction of beta-amyloid induces tau hyperphosphorylation and decreases the solubility of tau in N2a cells.
Although neurofibrillary tangles and senile plaques have been identified as the hallmark pathological changes in the brain of Alzheimer's disease (AD), the relationship between them is still not fully understood. In the present study, we have studied the effect of endogenously overproduced amyloid beta (Abeta) on tau by using wild type amyloid precursor protein (APP) transfected (N2a/APP695), or Swedish mutant APP plus Delta9 deleted presenilin-1 co-transfected (N2a/APPswe.Delta9) and APP vector transfected (N2a/vector) cell lines. We measured the secreted and intracellular Abeta, including Abeta(1-40) and Abeta(1-42), by Sandwich ELISA assay. It was shown that the levels of Abeta were increased time-dependently in N2a/APP695 and N2a/APPswe.Delta9 but not in N2a/vector upon butyric acid (BA) treatment. Compared with N2a/vector cells, tau in N2a/APP695 and N2a/APPswe.Delta9 cells was not extracted by RIPA buffer, and the SDS-extracted tau protein was hyperphosphorylated at Tau-1 and PHF-1 epitopes upon BA treatment. Obvious accumulation of the hyperphosphorylated tau in N2a/APP695 and N2a/APPswe.Delta9 cells was observed at 48 h after BA treatment. The total level of the extracted tau was reduced in N2a/APP695 and N2a/APPswe.Delta9 lines compared with N2a/vector cells by Western blot, and this reduction of total tau was also detected by immunofluorescence staining. No obvious alteration of tau mRNA was observed in both N2a/APP695 and N2a/APPswe.Delta9 cells compared with N2a/vector. This study provides direct evidence demonstrating that endogenously overproduced Abeta not only induces tau hyperphosphorylation but also decreases the level and solubility of tau in N2a cell lines.[1]References
- Endogenous overproduction of beta-amyloid induces tau hyperphosphorylation and decreases the solubility of tau in N2a cells. Wang, Y.P., Wang, X.C., Tian, Q., Yang, Y., Zhang, Q., Zhang, J.Y., Zhang, Y.C., Wang, Z.F., Wang, Q., Li, H., Wang, J.Z. Journal of neural transmission (Vienna, Austria : 1996) (2006) [Pubmed]
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