Overactivated mitogen-activated protein kinase by anisomycin induces tau hyperphosphorylation.

One of the pathological feathers of Alzheimer's disease (AD) is neurofibrillary tangles (NFTs), which consist of paired helical filaments (PHFs) formed by hyperphosphorylated microtubule-associated protein tau. To study the role of mitogen-activated protein kinase (MAPK) in tau hyperphosphorylation and the underlying mechanism, wild type mouse neuroblastoma cells (N2a) were dealt with different concentrations (0.1 microg/mL, 0.2 microg/mL and 0.4 microg/mL) of anisomycin (an activator of MAPK) for 6 h. The relationship between MAPK activity and tau phosphorylation at some Alzheimer-sites was analyzed, and the activities of protein kinase A (PKA) and glycogen synthase kinase-3 (GSK-3) were detected. The results showed that anisomycin activated MAPK in a dose-dependent manner, but tau hyperphosphorylation at Ser-198/199/202 and Ser-396/404 sites was only observed when the concentration of anisomycin was at the level of 0.4 microg/mL, and the alteration of tau phosphorylation at Ser-214 showed no significant difference in different groups. 0.2 microg/mL and 0.4 microg/mL of anisomycin led to an increase in the activity of GSK-3, respectively, but had no effect on the activity of PKA. Lithium chloride, a specific inhibitor of GSK-3, completely abolished the anisomycin-induced elevation of tau phosphorylation without any effect on the activity of MAPK. In conclusion, overactivation of MAPK up to a certain degree induces tau hyperphosphorylation at Ser-198/199/202 and Ser-396/404 sites, and this is probably related to the effect of activated GSK-3 by MAPK.