Cell-based ELISA Assay: The ELISA portion of the assay was performed in a black Maxisorp 96-well plate that was coated overnight at 4° C. with 100 uL/well of the cell lysate (1:10 dilution of the lysate with PBS containing protease inhibitors, phosphatase inhibitors, and PMSF). The following day the wells were washed 3 times with 300 uL/well of Wash buffer (Tris-buffered saline with 0.1% Tween 20). The wells were blocked with 100 ul/well Blocking buffer (Tris buffered saline w/0.05% Tween 20 and 2.5% Bovine serum albumin). Each well was then washed two times with 300 uL/well of wash buffer. The anti O-GlcNAc antibody RL-2 (Abeam, Cambridge, Mass.), diluted 1:1000 in blocking buffer, was added at 100 uL/well. The plate was sealed and incubated at 37° C. for 2 h with gentle shaking. The wells were then washed 3-times with 300 uL/well wash buffer. To detect the amount of RL-2 bound horse-radish peroxidase (HRP) conjugated goat anti-mouse secondary antibody (diluted 1:3000 in blocking buffer) was added at100 uL/well. The plate was incubated for 60 min at 37° C. with gentle shaking. Each well was then washed 3-times with 300 uL/well wash buffer. The detection reagent was added, 100 uL/well of Amplex Ultra RED reagent (prepared by adding 30 uL of 10 mM Amplex Ultra Red stock solution to 10 mL PBS with 18 uL 3% hydrogen peroxide, H2O2). The detection reaction was incubated for 15 minutes at room temperature and then read with excitation at 530 nm and emission at 590 nm.
null: Enzymatic reactions were carried out in a reaction containing 50 mM NaH2PO4, 100 mM NaCl and 0.1% BSA (pH 7.0) using 2 mM 4-Methylumbelliferyl N-acetyl-β-D-glucosaminide dihydrate (Sigma M2133) dissolved in ddH2O, as a substrate. The amount of purified human O-GlcNAcase enzyme used in the reaction was 0.7 nM. Test compound of varying concentrations was added to the enzyme prior to initiation of the reaction. The reaction was performed at room temperature in a 96-well plate and was initiated with the addition of substrate. The production of fluorescent product was measured every 60 sec for 45 min with a Tecan Infinite M200 plate-reader with excitation at 355 nM and emission detected at 460 nM, with 4-Methylumbelliferone (Sigma M1381) used to produce a standard curve.
Inhibition of human beta hexosaminidase assessed as inhibitory constant using 4-methylumbelliferyl N-acetyl-beta-D-glucosaminide dihydrate as substrate measured every 60 sec for 45 mins by fluorescence spectrophotometry