APP and Alzheimer disease: Two main neuropathological hallmarks, derived from altered proteostasis, can be found in the brain of AD patients, namely, senile plaques containing amyloid-β peptide (Aβ), which is derived from Aβ precursor protein (APP) processing, and intraneuronally located neurofibrillary tangles (NFTs) of hyperphosphorylated tau protein [2].