Tau phosphorylation by glycogen synthase kinase 3β modulates enzyme acetylcholinesterase expression

In Alzheimer's disease (AD), the enzyme acetylcholinesterase (AChE) co-localizes with hyperphosphorylated tau (P-tau) within neurofibrillary tangles. Having demonstrated that AChE expression is increased in the transgenic mouse model of tau Tg-VLW, here we examined whether modulating phosphorylated tau levels by over-expressing wild-type human tau and glycogen synthase kinase-3 beta (GSK3 beta) influences AChE expression. In SH-SY5Y neuroblastoma cells expressing higher levels of P-tau, AChE activity and protein increased by (20% +/- 2%) and (440% +/- 150%), respectively. Western blots and qPCR assays showed that this increment mostly corresponded to the cholinergicACHE-Tvariant, for which the protein and transcript levels increased similar to 60% and similar to 23%, respectively. Moreover, in SH-SY5Y cells differentiated into neurons by exposure to retinoic acid (10 mu M), over-expression of GSK3 beta and tau provokes an imbalance in cholinergic activity with a decrease in the neurotransmitter acetylcholine in the cell (45 +/- 10%). Finally, we obtained cerebrospinal fluid (CSF) from AD patients enrolled on a clinical trial of tideglusib, an irreversible GSK3 beta inhibitor. In CSF of patients that received a placebo, there was an increase in AChE activity (35 +/- 16%) respect to basal levels, probably because of their treatment with AChE inhibitors. However, this increase was not observed in tideglusib-treated patients. Moreover, CSF levels of P-tau at the beginning measured by commercially ELISA kits correlated with AChE activity. In conclusion, this study shows that P-tau can modulate AChE expression and it suggests that AChE may possibly increase in the initial phases of AD.

Automated summary

This study demonstrates that P-tau can modulate AChE expression, and suggests that AChE may increase in the initial phases of AD.