HTT and Alzheimer disease: The main protein aggregates related to proteinopathies are: amyloid β (Aβ) peptide and Tau protein in AD [68,69,70,71]; α-synuclein (α-syn) in PD [72,73,74], transactive response DNA-binding protein of 43 kDa (TDP-43) in AD and ALS [61,75,76]; Cu, Zn-superoxide dismutase (SOD1) in ALS [77,78]; and Huntingtin protein (Htt) in HD [50,79,80].