Fig. 1.

Sterol specificity of ABCA1. A: GC-MS analysis of apoA-I-mediated sterol release. HEK/hABCA1 cells were incubated with apoA-I (10 μg/ml). Lipids were extracted from medium, saponified, and analyzed by GC-MS, as described in Materials and Methods. The peaks of epicoprostanol [internal standard (I.S.)], cholesterol (Chol, peak 1), and lanosterol (Lan, peak 6) are indicated by arrowheads. Other minor peaks (2–5 and 7) are shown in the inset and described in Table 1. B–G: HEK293 and HEK/hABCA1 (B, C), and WT and Abca1^−/− (D, E) MEFs were treated with 1 μg/ml of TO901317 for 24 h, and differentiated THP-1 cells (F, G) were incubated with or without apoA-I in the presence of [³H]acetate for 8 h in 6-well plates. Lipids were extracted from medium and cells, and were saponified. Sterols were analyzed by TLC. Results are shown as cpm or dpm of [³H]sterol per milligram of cell protein (B, D, F) or as percent release relative to each [³H]sterol synthesized [medium/(medium + cell) × 100] (C, E, G). Error bars represent SD (n = 3).