FIGURE 5.

UbxD8 is an essential co-factor of gp78. A, cells transfected with plasmids expressing the indicated UBX-containing proteins were lysed in the Nonidet P-40 lysis buffer. The UBX-containing proteins were immunopurified with FLAG beads. The purified proteins complexes were analyzed by immunoblotting with the indicated antibodies. B, cells stably expressing TCRα-YFP were transfected with either control or UbxD8-specific shRNA plasmid together with a construct expressing hemagglutinin (HA)-tagged ubiquitin. The cells were treated with either DMSO as control or with the proteasome inhibitor MG132 (10 μm, 12 h). TCRα was immunoprecipitated from the cell extracts under a denaturing condition for analysis by immunoblotting. WCE, whole cell extract.