FIGURE 3.

CUE domain of AUP1 mediates interaction with ER quality control proteins and terminally misfolded proteins. A, HeLa cells were transfected with empty vector or one of the HA-AUP1 WT or mutant constructs. HA-AUP1 was recovered with 3F10 (anti-HA) antibody from digitonin lysates. Immunoblotting (IB) with antibodies for the indicated proteins showed the presence of endogenous proteins in the total cell lysates and immunoprecipitates (IP). * indicates cross-reactive proteins and ** indicates degradation product of UBC6e. B, HeLa cells were transfected with the NHK variant of α1-antitrypsin and one of the AUP1 WT or mutant constructs as indicated. These cells were incubated with 5 μm ZL₃VS overnight. NHK was recovered from Nonidet P-40 lysates, and the content of AUP1 in total cell lysates and immunoprecipitates was determined by immunoblotting with an anti-AUP1 antibody. Both endogenous and transiently introduced AUP1s are present in the immunoblots. C, same experiment as in B was repeated with RI₃₃₂-HA instead of NHK.