出版社：American Society for Biochemistry and Molecular Biology
摘要：The assembly of HDL by helical apolipoprotein and cellular lipidwas studied using HEK293 cells to which ecdysone-inducible humanABCA1 or human ABCA7 was transfected. Expression of both ABCA1and ABCA7 was induced linearly proportional to ponasterone Aconcentration in the medium. In the experimental conditionsused, the ABC protein expression levels limited the rate oflipid release when the apolipoprotein concentration was high,and the apolipoprotein concentration was rate-limiting whenthe ABC protein expression levels were high. When ABCA1 expressionincreased in conditions in which it was rate-limiting, relativecholesterol content to phospholipid increased in the HDL produced.In contrast, it was constant when ABCA7 expression increased.To investigate the background mechanism, the HDL particles wereanalyzed by density gradient ultracentrifugation and high performancelipid chromatography. The ABCA1-mediated reaction produced twodistinct HDLs, large cholesterol-rich and small cholesterol-poorparticles, and the ABCA7-mediated reaction generated mostlysmall cholesterol-poor particles. The increase of HDL assemblywith the increase of ABCA1 expression was predominant in largecholesterol-rich particles, whereas only small cholesterol-poorHDL increased as ABCA7 expression increased.
We conclude that ABCA1 generates cholesterol-rich and cholesterol-poorHDL and that the former is more prominently dependent on theincrease of ABCA1 expression. ABCA7 produces this HDL subfractiononly as a very minor component.Abbreviations: apoA-I, apolipoprotein A-I; DF, 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12 medium; GFP, green fluorescent protein
Supplementary key words ATP binding cassette transporter A1 • ATP binding cassette transporter A7 • cholesterol • ecdysone-inducible
