Microglial activation is a key pathogenic process at the onset of Alzheimer’s disease (AD). Identifying regulators of microglial activation bears great potential in elucidating causes and mechanisms of AD and determining candidates for early intervention. Previous studies demonstrate abnormal elevation of glutaminase C (GAC) in HIV-infected or immune-activated microglia. However, whether GAC elevation causes microglial activation remains unknown. In this study, we found heightened expression levels of GAC in early AD mouse brain tissues compared with those in control littermates. Investigations on an in vitro neuroinflammation model revealed that GAC is increased in primary mouse microglia following pro-inflammatory stimulation. To model GAC elevation we overexpressed GAC by plasmid transfection and observed that GAC-overexpression shift the microglial phenotype to a pro-inflammatory state. Treatment with BPTES, a glutaminase inhibitor, reversed LPS-induced microglial activation and inflammation. Furthermore, we discovered that GAC overexpression in mouse microglia increased exosome release and changed exosome content, which includes specific packaging of pro-inflammatory miRNAs that activate microglia. Together, our results demonstrate a causal effect of GAC elevation on microglial activation and exosome release, both of which promote the establishment of a pro-inflammatory microenvironment. Therefore, GAC may have important relevance to the pathogenesis of AD.

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APP misexpression plays a crucial role in triggering a complex pathological cascade, leading to Alzheimer’s disease (AD). But how the expression of APP is regulated in pathological conditions remains poorly understood. In this study, we found that the exosomes isolated from AD mouse brain promoted APP expression in neuronal N2a cells. Moreover, exosomes derived from N2a cells with ectopic expression of APP (APP-EXO) also induced APP dysregulation in normal N2a cells. Surprisingly, the effects of APP-EXO on APP expression in recipient cells were not mediated by the direct transferring of APP gene products. Instead, the effects of APP-EXO were highly likely mediated by the reduction of the expression levels of exosomal miR-185-5p. We found that the 3′UTR of APP transcripts binds to miR-185-5p, therefore inhibiting the sorting of miR-185-5p to exosomes. N2a cell-derived exosomes with less amount of miR-185-5p exert similar roles in APP expression to APP-EXO. Lastly, we demonstrated a significant decline of serum exosomal miR-185-5p in AD patients and AD mice, versus the corresponding controls. Together, our results demonstrate a novel mechanism in the exosome-dependent regulation of APP, implying exosomes and exosomal miRNAs as potential therapeutic targets and biomarkers for AD treatment and diagnosis, respectively.