APP and Alzheimer disease: Interestingly, within the group of proteins that exhibited the most significant loss, we found proteins implicated in key cellular functions and pathways, namely, regulators of synapse stability/organization, fatty acid / lipid metabolism, related to cell bioenergetics, and, curiously, related to AD pathology or associated with Amyloid β, a proteolytic cleavage product of APP (amyloid precursor protein) whose fibrillar form is the main component of amyloid plaques found in the brains of AD patients (reviewed in Chen et al., 2017).