APP and Alzheimer disease: Aβ42 is a key playerin AD pathogenesis because Aβ42is more hydrophobic and stickier than Aβ40 and is overproducedin AD because of genetic mutations in the APP gene or other genes.Aβ42 fibrils readily clump together to form amyloid plaques. BACE-1 acts as the β-secretase enzymeby cleaving the transmembrane APP to release the β-stubs.