FIGURE 3.

TIR-199 inhibits the proteasome activity in vitro. The inhibitory effect of increasing concentrations of TIR-199 (0–5 μm) on the CT-L, C-L, and T-L catalytic subunit activities of the constitutive proteasome (A) and immunoproteasome (B) were measured, using luminogenic substrates as described under “Experimental Procedures.” BTZ was used as a positive control (0.01 μm). The relative light units for each catalytic subunit activity were expressed as Remaining Activity in %, where 100% activity represents the control (untreated proteasome). Data represent the average of three independent experiments (n = 3); bars, mean ± S.E. (error bars).