Fibrillar Aβ triggers microglial proteome alterations and dysfunction in Alzheimer mouse models

Microglial dysfunction is a key pathological feature of Alzheimer´s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their consequences for microglial function. Here, we performed an in-depth proteomic characterization of microglia in two AD mouse models, the overexpression APPPS1 and the knock-in AppNL-G-F (APP-KI) model. Proteome changes were followed from pre-deposition to early, middle and advanced stages of amyloid plaque pathology, revealing a large panel of Microglial Amyloid Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations triggered by Adeposition. We demonstrate that the occurrence of MARPs coincided with the deposition of fibrillar A, recruitment of microglia to amyloid plaques and phagocytic dysfunction. While the proteomic and functional microglial changes were already markedly seen in 3 months old APPPS1 mice, they were delayed in the APP-KI model that generates substantially less fibrillar A. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.