Unexpectedly, we found that the upregulated genes were enriched for AD related pathways including the APP secretase genes, PSEN1 and BACE1 (Table S6), which prompted us to measure the secreted Aβ levels, including Aβ (1–40) and Aβ (1–42), in our iGlut/mAst co-cultures by ELISA. Here, CTSB is linked to Alzheimer disease.