Triggering receptor expressed on myeloid cell 2 (TREM2) is linked to risk of neurodegenerative disease. However, the function of TREM2 in neurodegeneration is still not fully understood. Here, we investigated the role of microglial TREM2 in TAR DNA-binding protein 43 (TDP-43)-related neurodegeneration using virus-mediated and transgenic mouse models. We found that TREM2 deficiency impaired phagocytic clearance of pathological TDP-43 by microglia and enhanced neuronal damage and motor impairments. Mass cytometry analysis revealed that human TDP-43 (hTDP-43) induced a TREM2-dependent subpopulation of microglia with high CD11c expression and phagocytic ability. Using mass spectrometry (MS) and surface plasmon resonance (SPR) analysis, we further demonstrated an interaction between TDP-43 and TREM2 in vitro and in vivo as well as in human tissues from individuals with amyotrophic lateral sclerosis (ALS). We computationally identified regions within hTDP-43 that interact with TREM2. Our data highlight that TDP-43 is a possible ligand for microglial TREM2 and that this interaction mediates neuroprotection of microglia in TDP-43-related neurodegeneration.
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