Effect of inhibitors on degradation of short-lived proteins in multiple myeloma cells.

Degradation of short-lived proteins was analyzed after 1-h pulse labeling with [3H]Leu followed by 1-h chase. Total degradation was calculated as % of [3H]Leu incorporated during released in the TCA-soluble fraction during 1 h chase. Treatment with inhibitors was performed during pulse labeling.% inhibition of degradation (at 1 h) was calculated as [1–(%TCA soluble radioactivity in the presence of inhibitor)/(% TCA soluble in the absence of inhibitor)]×100%. Inhibition of proteasomal degradation was determined by dividing inhibition by bortezomib by inhibition by ZL3ek.Values are averages ± SEM of n independent experiments for inhibition of protein degradation. Data on viable cells are from Fig. 1B, where errors are shown.