Inhibition of tubulin and actin degradation by proteosome inhibitor MG132. Mouse reticulocytes were cultured for 48 hours in the presence of the proteasome inhibitor MG132 (10μM) or an equivalent volume of the solvent, DMSO. Western blots of SDS-PAGEs of total cellular protein were probed with antibodies against tubulin, actin, CD71 and β-spectrin. CD71 serves as a positive control and β-spectrin as a negative control.