Proposed model for the combined effects of cholinesterases on Alzheimer’s disease progression. Note that both AChE-R and BChE can potentially attenuate Aβ oligomerization and its toxic effects, whereas AChE-S inversely promotes these processes, accelerating neurodegeneration. BChE-K is further impaired in its ability to attenuate fibril formation and may thus also contribute to neurodegeneration. N-AChE-S additionally promotes neurodegeneration of cholinergic neurons by the induction of apoptosis and tau hyperphosphorylation.