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

Microglial dysfunction is a key pathological feature of Alzheimers disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their functional consequences. Here, we performed an in-depth and time-resolved proteomic characterization of microglia in two mouse models of amyloid Aβ pathology, the overexpression APPPS1 and the knock-in APP-NL-G-F (APP-KI) model. We identified a large panel of Microglial Aβ Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations during early, middle and advanced stages of Aβ deposition. Although both mouse models display severe microglial alterations at late stages of amyloid pathology, MARP signatures occur earlier in the APPPS1 mice. Strikingly, the kinetic differences in proteomic profiles correlated with the presence of fibrillar Aβ rather than dystrophic neurites, suggesting that fibrillar Aβ aggregates are the main drivers of the AD-associated microglial phenotype and the observed functional decline. 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.