Using the Tau35 mouse model and SH‐SY5Y human neuroblastoma cells stably expressing Tau35 or full‐length tau, we assessed protein degradation and lysosomal function via Western blotting, proteomics of lysosome‐enriched brain fractions, cathepsin activity assays, endocytosis/proteolysis assays, and live‐cell imaging using LysoTracker. Here, MAPT is linked to neuroblastoma.