Differential Interaction With Trem2 Modulates Microglial Uptake Of Modified A Beta Species

Rare coding variants of the microglial triggering receptor expressed on myeloid cells 2 (TREM2) confer an increased risk for Alzheimer's disease (AD) characterized by the progressive accumulation of aggregated forms of amyloid beta peptides (A beta). A beta peptides are generated by proteolytic processing of the amyloid precursor protein (APP). Heterogeneity in proteolytic cleavages and additional post-translational modifications result in the production of several distinct A beta variants that could differ in their aggregation behavior and toxic properties. Here, we sought to assess whether post-translational modifications of A beta affect the interaction with TREM2. Biophysical and biochemical methods revealed that TREM2 preferentially interacts with oligomeric A beta, and that phosphorylation of A beta increases this interaction. Phosphorylation of A beta also affected the TREM2 dependent interaction and phagocytosis by primary microglia and in APP transgenic mouse models. Thus, TREM2 function is important for sensing phosphorylated A beta variants in distinct aggregation states and reduces the accumulation and deposition of these toxic A beta species in preclinical models of Alzheimer's disease.