FIGURE 7.

ATPase activity of ABCA1 is required for its ability to facilitate retrograde cholesterol transport. A, induction of ABCA1 expression by mifepristone. BHK cells stably transfected with vector or vector harboring WT-ABCA1 or ABCA1-MM cDNA (BHK/mock, BHK/WT-ABCA1, and BHK/ABCA1-MM respectively) cells were incubated with the indicated concentrations of mifepristone for 18 h. ABCA1 expression was examined by immunoblot. B and C, apoA-I-dependent cholesterol and PL efflux. BHK/mock, BHK/WT-ABCA1, and BHK/ABCA1-MM cells were incubated with or without apoA-I (5 μg/ml) in the absence or presence of 5 nm mifepristone for 18 h, as indicated. Amounts of cholesterol (B) and PL (C) released into medium were measured. Subtracted values are shown. Data represent means ± S.D. (n = 3). D, PM-to-ER cholesterol transport. BHK cells treated without or with 5 nm mifepristone were pulse-labeled with [³H]cholesterol and then chased for 3 h. ABCA1-specific esterification was calculated by subtracting counts of mifepristone-untreated cells. Data represent means ± S.D. (n = 3). #, p < 0.01 by one-way ANOVA with Tukey-Kramer post hoc test. ns, not significant.