Quantitative proteomics reveals that PEA15 regulates astroglial Aß phagocytosis in an Alzheimer's disease mouse model.

ABSTRACT

Amyloid-beta (Aß) deposition plays a crucial role in the progression of Alzheimer's disease (AD). The Aß deposited extracellularly can be phagocytosed and degraded by surrounding activated astrocytes, but the precise mechanisms underlying Aß clearance mediated by astrocytes remain unclear. In this study, we performed tandem mass tag-based quantitative proteomic analysis on the cerebral cortices of 5-month-old APP/PS1 double-transgenic mice. Among the 2668 proteins quantified, 35 proteins were upregulated and 12 were downregulated, with most of these proteins being shown here for the first time to be differently expressed in the APP/PS1 mouse. The altered proteins were involved in molecular transport, lipid metabolism, autophagy, inflammation, and oxidative stress. One specific protein, PEA15 (phosphoprotein enriched in astrocytes 15 kDa) upregulated in APP/PS1 mice, was verified to play a critical role in astrocyte-mediated Aß phagocytosis. Furthermore, PEA15 levels were determined to increase with age in APP/PS1 mice, indicating that Aß stimulated the upregulation of PEA15 in the APP/PS1 mouse. These results highlight the function of PEA15 in astrocyte-mediated Aß phagocytosis, and thus provide novel insight into the molecular mechanism underlying Aß clearance. The protein-expression profile revealed here should offer new clues to understand the pathogenesis of AD and potential therapeutic targets for AD. BIOLOGICAL SIGNIFICANCE: Activated astrocytes are known to clear the Aß deposited in the extracellular milieu, which is why they play a key role in regulating the progression of Alzheimer's disease (AD). However, the molecular mechanism underlying astrocyte-mediated Aß phagocytosis and degradation remains unclear. By performing tandem mass tag-based quantitative proteomic analysis, we identified 47 proteins that were differentially expressed in APP/PS1 double-transgenic. To our knowledge, this is the first time most of these proteins have been reported to exhibit altered expression in the mouse model of AD. Furthermore, our results indicate that one of the proteins upregulated in the APP/PS1 mouse, PEA15 (phosphoprotein enriched in astrocytes 15 kDa), regulates astroglial phagocytosis of Aß. Our findings provide new insights into the molecular mechanism underlying Aß clearance in AD. The altered profile of protein expression in APP/PS1 mice described here should offer valuable clues to understand the pathogenesis of AD and facilitate the identification of potential targets for the treatment of AD.