Figure 5.

Effect of tunicamycin injection on the level of apoB-100 in the liver of ATF6α +/+ and −/− mice. (A) Tunicamycin (Tm) was injected into ATF6α +/+ and −/− mice as described in Figure 1A. Microsomes were prepared from livers at the indicated time points after injection. Aliquots (100 μg) of microsomal lysates were analyzed by immunoblotting using anti-apoB-100 antibody. The results of four independent experiments are shown. Bottom right, intensity of each band was quantified, normalized with the respective value at 0 h, and plotted against time after tunicamycin injection. (B) Top, 100-μg aliquots of microsomal lysates prepared as described in A were digested with (+) or without (−) endo H and then analyzed by immunoblotting using anti-ATF6β antibody. The migration positions of pATF6β(P) and pATF6β(P*), the unglycosylated form of pATF6β(P), are indicated. Bottom, 100-μg aliquots of microsomal lysates prepared as described in A were analyzed by immunoblotting using anti-HSP47 antibody. (C) HepG2 cells transfected with vector alone (Mock) or vector to express a dominant-negative form of ATF6α (ATF6αDN) were treated with cycloheximide (CHX) for the indicated periods. Cell lysates were prepared and analyzed by immunoblotting using antibody to ApoB-100 or actin. Intensity of each band was quantified, normalized with the respective value at 0 h, and plotted against time of cycloheximide treatment. Values are presented as the mean ± SEM (n = 3).