APP and Alzheimer disease: Given these observations, the previous links between GAPDH, exosomes and β-amyloid plaques (Dar et al, 2021; Yuyama and Igarashi, 2017; Itakura et al, 2015; Lazarev et al, 2021) and the proposed role of defective endosomal trafficking in initiating AD pathology (Cataldo et al, 2000), we tested the functions of transmembrane APP and its cleavage products (Fig. 3A) in SC DCG biogenesis and endosomal trafficking.