The half-life of pro-αIIb is prolonged in the presence of proteasome inhibitors. (A-C) Pulse-chase analyses were performed as described in Figure 1 on HEK293 cells stably expressing αIIb alone in the presence of DMSO (vehicle control; A) or either of the proteasome inhibitors MG132 (B), or PSI (C). (D) The densities of the pro-αIIb bands from a representative experiment are plotted as a percentage of the density at 3 hours after the chase.