Tyr682 in the Intracellular Domain of APP Regulates Amyloidogenic APP Processing In Vivo

Alessia P M Barbagallo,Luciano D'Adamio,Luca Giliberto,Richard Weldon,Dawang Zhou,Oded Foreman,Robert Tamayev,Maria A Deli

doi:10.1371/journal.pone.0015503

Alessia P M Barbagallo, Luciano D'Adamio + Show 6 more

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https://doi.org/10.1371/journal.pone.0015503

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Abstract

BackgroundThe 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 FindingsTo this end, we have generated an APP Y682G knock-in (KI) mouse to help dissect the role of APP Tyr682 in 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/SignificanceTogether, 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.

Highlights

The most common form of dementia in the world is Alzheimer’s disease (AD), affecting about 1% of the human population by aged 65, and rising to 35–40% after age 85
Generation of Ab-precursor protein (APP) Y682G and T668A Mutant Mice The targeting strategy for the generation of the APP KI mice entailed the replacement of APP exon 16 with exon 16 carrying the Y682G or T668A mutation (Fig. 1A)
APP Y682G mutation in mice clearly results in a large redistribution of APP towards nonamyloidogenic pathway; sAPP-a and C83 are greatly increased while sAPP-b and Ab40 are decreased (Fig. 2), demonstrating the necessary role of the C-terminal in normal activity of the amyloidogenic pathway in the brain and consistent with the results observed in vitro

Summary

Introduction

The most common form of dementia in the world is Alzheimer’s disease (AD), affecting about 1% of the human population by aged 65, and rising to 35–40% after age 85. Evidence points to a key role for misfolded amyloidogenic Ab peptides in the pathogenesis of AD (amyloid cascade hypothesis). Ab peptides are generated during amyloidogenic processing of Ab-precursor protein (APP). When APP is cleaved by b-secretase, the soluble ectodomain (sAPPb) is released extracellularly whilst the 99 amino acid C-terminal fragment (C99) remains membrane bound. In this pathway APP is cleaved by a-secretase in the Ab sequence producing the soluble ectodomain (sAPPa) and the membrane bound 83 amino acid C-terminal fragment (C83). The pathogenesis of Alzheimer’s disease is attributed to misfolding of Amyloid-b (Ab) peptides. Ab is generated during amyloidogenic processing of Ab-precursor protein (APP). Another characteristic of the AD brain is increased phosphorylation of APP amino acid Tyr682.

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