BACE1 and Alzheimer disease: Decreased BACE1 levels were protected by inhibiting lysosomal acidification or endocytosis using bafilomycin A1 or chlorpromazine in siSNX4-transfected cells (Additional file 5: Figure S5), which may explain how BACE1 is not decreased in the brains of 24-month-old mice or in late-stage AD brains.