Tyr⁶⁸² in the intracellular domain of APP regulates amyloidogenic APP processing in vivo

Background: The pathogenesis of Alzheimer's disease is attributed to misfolding of Amyloid-β (Aβ) peptides. Aβ is generated during amyloidogenic processing of Aβ-precursor protein (APP). Another characteristic of the AD brain is increased phosphorylation of APP amino acid Tyr⁶⁸². Tyr⁶⁸² is part of the Y⁶⁸²ENPTY⁶⁸⁷ motif, a docking site for interaction with cytosolic proteins that regulate APP metabolism and signaling. For example, normal Aβ generation and secretion are dependent upon Tyr⁶⁸² in vitro. However, physiological functions of Tyr⁶⁸² are unknown. Methodology/Principal Findings: To this end, we have generated an APP Y682G knock-in (KI) mouse to help dissect the role of APP Tyr⁶⁸²in vivo. We have analyzed proteolytic products from both the amyloidogenic and non-amyloidogenic processing of APP and measure a profound shift towards non-amyloidogenic processing in APP KI mice. In addition, we demonstrate the essential nature of amino acid Tyr⁶⁸² for the APP/Fe65 interaction in vivo. Conclusions/Significance: Together, these observations point to an essential role of APP intracellular domain for normal APP processing and function in vivo, and provide rationale for further studies into physiological functions associated with this important phosphorylation site.