HeLa cells have been stably transfected with HA-tagged α-TCR. (A) Immunofluorescent labeling with HA11 antibody reveals that α-TCR is expressed mostly in the ER as seen by the colocalization with the ER marker Grp94 (upper row), while it does not colocalize with the Golgi marker TGN46 (lower row).Ubiquitin labels nuclei and cytosol, but not the ER, therefore it does not colocalize with α-TCR. The bar indicates 5 μm. (B) Western blotting showing the effects of a time course of different drugs on cellular levels of α-TCR; While MG132 induces an accumulation of αTCR, treatment with either tunicamycin or brefeldin A induces depletion of αTCR from cells, which is mediated by a proteasome-dependent process as evidenced by the effect of MG132.