ABCA1 and ABCG1 synergize to mediate cholesterol export to apoA-I.
OBJECTIVE
To study the acceptor specificity for human ABCG1 (hABCG1)-mediated cholesterol efflux.


RESULTS
Cells overexpressing hABCG1 were created in Chinese Hamster Ovary (CHO-K1) cells and characterized in terms of lipid composition. hABCG1 expressed in these cells formed homodimers and was mostly present intracellularly. Cholesterol efflux from hABCG1 cells to HDL2 and HDL3 was increased but not to lipid-free apolipoproteins. A range of phospholipid containing acceptors apart from high-density lipoprotein (HDL) subclasses were also efficient in mediating ABCG1-dependent export of cholesterol. Importantly, a buoyant phospholipid-containing fraction generated from incubation of lipid-free apoA-I with macrophages was nearly as efficient as HDL2. The capacity of acceptors to induce ABCG1-mediated efflux was strongly correlated with their total phospholipid content, suggesting that acceptor phospholipids drive ABCG1-mediated efflux. Most importantly, acceptors for ABCG1-mediated cholesterol export could be generated from incubation of cells with lipid-free apoA-I through the action of ABCA1 alone.


CONCLUSIONS
These results indicate a synergistic relationship between ABCA1 and ABCG1 in peripheral tissues, where ABCA1 lipidates any lipid-poor/free apoA-I to generate nascent or pre-beta-HDL. These particles in turn may serve as substrates for ABCG1-mediated cholesterol export.
Gelissen
Ingrid C
IC
Centre for Vascular Research, School of Medical Sciences, University of New South Wales, Kensington, Australia.
Harris
Matthew
M
Rye
Kerry-Anne
KA
Quinn
Carmel
C
Brown
Andrew J
AJ
Kockx
Maaike
M
Cartland
Sian
S
Packianathan
Mathana
M
Kritharides
Leonard
L
Jessup
Wendy
W
D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism* / Q000494:pharmacology; D050197:Atherosclerosis / Q000378:metabolism; D016466:CHO Cells; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000493:pharmacokinetics*; D006224:Cricetinae; D019281:Dimerization; D006801:Humans; D007948:Leukemia, Monocytic, Acute; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D014162:Transfection; D014316:Tritium
C577836:ABCA1 protein, human; C419353:ABCG1 protein, human; D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D010743:Phospholipids; D014316:Tritium; D002784:Cholesterol