Intact cell-based chymotrypsin-like, trypsin-like, and caspase-like proteasome activities

An intact cell-based Proteasome-Glo assay kit (Promega, Madison, WI) was used to measure basal and piperlongumine-induced proteasome activity according to the manufacturer's instructions. MM cells were exposed to piperlongumine for 24 h, and 20,000 cells were collected from each well for detection. After 10 min of incubation with an equal volume of Proteasome-Glo cell based reagent, luminescence was measured with a GloMAX 96 Microplate Luminometer (Promega).