Tyrosine Binding Protein Sites Regulate the Intracellular Trafficking and Processing of Amyloid Precursor Protein through a Novel Lysosome-Directed Pathway

The amyloid hypothesis posits that the production of beta-amyloid (A beta) aggregates leads to neurodegeneration and cognitive decline associated with AD. A beta is produced by sequential cleavage of the amyloid precursor protein (APP) by beta- and gamma-secretase. While nascent APP is well known to transit to the endosomal/lysosomal system via the cell surface, we have recently shown that APP can also traffic to lysosomes intracellularly via its interaction with AP-3. Because AP-3 interacts with cargo protein via interaction with tyrosine motifs, we mutated the three tyrosines motif in the cytoplasmic tail of APP. Here, we show that the YTSI motif interacts with AP-3, and phosphorylation of the serine in this motif disrupts the interaction and decreases APP trafficking to lysosomes. Furthermore, we show that phosphorylation at this motif can decrease the production of neurotoxic A beta 42. This demonstrates that reducing APP trafficking to lysosomes may be a strategy to reduce A beta 42 in Alzheimer's disease.