Fig. 5

Proteasome activity is lowered in REC1 cells. JeKo1 and REC1 cells were treated with MG-132 (500 nM), bortezomib (5 nM), or leupeptin (20 μM) for 4 h or vehicle, and protein extracts were prepared. Chymotrypsin-, trypsin- and caspase-like activities were monitored using Suc-LLVY-AMC, Z-ARR-AMC, and Z-LLE-AMC fluorogenic substrates, respectively with a reader plate (Victor X4, Perkin Elmer). For all culture conditions and substrates, the protease activity reached a plateau at 60 min. Fluorescence intensities (in arbitrary unit) were taken at that time and presented in the histograms. The experiments were done three times with triplicate samples. ***, p < 0.001 with the t-test