Down-regulation of Endogenous Amyloid Precursor Protein Processing due to Cellular Aging

Processing of amyloid precursor protein (APP) is a well acknowledged central pathogenic mechanism in Alzheimer disease. However, influences of age-associated cellular alterations on the biochemistry of APP processing have not been studied in molecular detail so far. Here, we report that processing of endogenous APP is down-regulated during the aging of normal human fibroblasts (IMR-90). The generation of intracellular APP cleavage products C99, C83, and AICD gradually declines with increasing life span and is accompanied by a reduced secretion of soluble APP (sAPP) and sAPPalpha. Further, the maturation of APP was reduced in senescent cells, which has been shown to be directly mediated by a…