al 2013). Most of these mutations are dominantly inherited and are positioned in the vicinity of β and γ secretase cleavage sites and, therefore, they influence APP proteolytic processing and/or aggregation. α- secretase is a third protease that prevents the formation of toxic Aβ peptides. The dysfunctional activity of these three proteases, results in Aβ accumulation, which stimulates diverse cell signalling pathways, and lastly resulting in synaptic degeneration, neuronal loss, and cognitive decline (Clement et. al …show more content…
The number of neurofibrillary tangles correlates well with the severity of impairment (Martone et. al, 2015). In mild AD cases considerable cytopathology were found in affect areas, that is, tau early aggregates, mature NFTs and neurites, all of them comprising phosphorylated tau at the Ser396-404 and Ser199-202- Thr205 sites (Mondragón et. al 2014). Neurofibrillary tangles is also a consequence of Aβ effects. Consistent with this view is the fact that all genes associated with familial AD play a role in Aβ processing (Martone et.al