PSA does not cleave Tau in cells. HEK293 cells expressing a tetracycline-inducible 2N4R Tau were transduced with lentivirus expressing GFP, PSA or its inactive mutant form (PSAx) and cultured for 48 hrs. Tetracycline (1 μg/ml) [Tet(+)] or vehicle (1:1 vol/vol water/ethanol) [Tet(-)] was added and cells were collected 12 hrs later. Cell extracts were subjected to SDS-PAGE, and analyzed by Western blot analysis with goat anti-hPSA (Chemicon) at 1:2000, and mouse anti-Tau antibody 5A6, at 1:4000. This was followed by incubation with peroxidase conjugated secondary antibodies and ECL Western Blotting detection.