Fig. 3

b-AP15 triggers cell apoptosis in ABC- and GCB-DLBCL by suppressing proteasome function. a b-AP15 inhibits USP14 and UCHL5 deubiquitinase activity in DLBCL cells. SU-DHL-4 and SU-DHL-2 cells incubated with b-AP15 over 3 h. The cells lysed with DUB buffer, then added 1 μM HA-Ub-VS and incubated in 37 °C 30 min. The protein levels of USP14 and UCHL5 were detected using western blot assay. b b-AP15 accumulates proteasome substrate proteins in DLBCL cells. Cells were treated with various doses of b-AP15 for 6 h. The protein levels of ubiquitin-proteins (Ubs) and p27 were detected using western blot assay. c b-AP15 has no obvious effect on the 20S proteasome peptidase activities in SU-DHL-4 and SU-DHL-2 cells. Cell lysate was treated with b-AP15, and then the C-like, T-like, CT-like activities at different times was recorded using the fluorogenic Z-LLE-AMC, Boc-LRR-AMC, Suc-LLVY-AMC substrates respectively. Mean ± SD (n = 3). d PARP cleavage occurs after proteasome inhibition with b-AP15 treatment. SU-DHL-4 and SU-DHL-2 cells were treated with the indicated dose of b-AP15 for the indicated duration. The protein levels of PARP and ubiquitin-proteins (Ubs) were detected with western blot assay