Figure 6. Lipid metabolism of HEK293 cells stably expressing ABCA17 or ABCA1.

(A, B) Release of cholesterol (A) and choline-phospholipids (B) from ABCA17- and ABCA1-expressing cells and untransfected control cells. Cells were cultured in the absence (open bars) or presence (closed bars) of 10 μg/ml apoA-I and 0.1% fatty acid-free BSA for 24 h, and released cholesterol and choline-phospholipids were measured. Values represent means±S.D. of three independent experiments; N.S., not significant. (C, D) Metabolic labelling of neutral lipids (C) and phospholipids (D) of ABCA17- and ABCA1-expressing cells and untransfected control cells. Intracellular ¹⁴C-labelled lipids and extracellular ¹⁴C-labelled lipids released from cells incubated with [¹⁴C]acetate for 72 h were separated by TLC, and representative autoradiographs are shown. Similar results were obtained from at least three independent experiments, and the radioactivity of each of the ¹⁴C-labelled lipid species quantified by FLA-5000 is shown in Table 1. ChoE, cholesteryl esters; FAE, fatty acid esters; TAG, triacylglycerols; FFA, non-esterified (free) fatty acids; Cho, cholesterol; DAG, diacylglycerols; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; SM, sphingomyelin; PS, phosphatidylserine; PA, phosphatidic acid; CL, cardiolipin; Lyso-PC, lyso-phosphatidylcholine.