APP and Alzheimer disease: Amyloid-β (Aβ) peptides are cleaved from the amyloid precursor protein (APP) into the peptides Aβ42 and Aβ40, which can form extracellular amyloid plaques.114,115 Tau proteins comprise highly soluble isoforms, while their hyperphosphorylation contributes to the development of neurofibrillary tangles (NFTs).116 Amyloid plaques are abundant in the CNS alongside NFTs in Alzheimer’s disease (AD), while NFTs are characteristic of PSP and CBS.117,118