IU1(IC50=4.7 μ M), a reversible, specific human USP14 proteasome inhibitor, can penetrate the cell.

IU1 binds specifically to the activated form of USP14. IU1 can potentially inhibit USP14 by preventing its docking on the proteasome, exhibiting little or no activity toward 8 other DUBs, IsoT, UCH37, BAP1, UCH-L1, UCH-L3, USP15, USP2, USP7. USP14 inhibition is rapidly established upon addition of IU1 and rapidly reversed upon its removal. IU1 inhibits USP14 induced chain trimming and decreases electrophoretic mobility of Ub-CCNB species. IU1 enhances proteasomal degradation of Ub-CCNB in the presence of USP14. IU1 promots degradation of tau and depletes TDP-43, ATXN3, and glial fibrillary acidic protein (GFAP) in proteotoxic mechanisms. [1]

High-throughput screening: Screening is conducted at the ICCB-Longwood screening facility. 10 μL of recombinant USP14 protein are dispensed into each well of a 384-well low volume plate in duplicate, using a Wellmate plate dispenser. 33.3?nL of compound from the library are pin-transferred into the wells using a Seiko pin transfer robotic system, followed by pre-incubation for about 30?min. The last two columns of each plate are used for positive and negative controls for the assay. To initiate the enzyme reaction, 10?μL of VS-proteasome plus Ub-AMC mixture are added to each well, using a Wellmate dispenser. Samples are then incubated for another 45?min. Ub-AMC hydrolysis is measured at Ex355/Em460 using an Envision plate reader. The final concentrations of USP14, VS-proteasome and Ub-AMC are 15?nM, 1?nM and 0.8 μM, respectively. The final concentration of test compound is approximately 17?μM. Enzymes and substrates are prepared in Ub-AMC assay buffer (50?mM Tris-HCl (pH?7.5), 1?mM EDTA, 1?mM ATP, 5 mM MgCl2, 1?mM DTT, and 1 mg/Ml ovalbumin).

MTT(Only for Reference)