APP and Alzheimer disease: For example, sortilin is genetically associated with Alzheimer’s disease (AD) (3, 4), regulates several aspects of amyloid precursor protein (APP) and amyloid-β (Aβ) trafficking and processing (5, 6, 7, 8, 9), and facilitates endocytic uptake of apolipoprotein E (9), the most important genetic risk factor for late-onset AD (10).