Lipid efflux by the ATP-binding cassette transporters ABCA1 and ABCG1.
Plasma levels of high-density lipoproteins (HDL) and apolipoprotein A-I (apoA-I) are inversely correlated with the risk of cardiovascular disease. One major atheroprotective mechanism of HDL and apoA-I is their role in reverse cholesterol transport, i.e., the transport of excess cholesterol from foam cells to the liver for secretion. The ATP-binding cassette transporters ABCA1 and ABCG1 play a pivotal role in this process by effluxing lipids from foam cells to apoA-I and HDL, respectively. In the liver, ABCA1 activity is one rate-limiting step in the formation of HDL. In macrophages, ABCA1 and ABCG1 prevent the excessive accumulation of lipids and thereby protect the arteries from developing atherosclerotic lesions. However, the mechanisms by which ABCA1 and ABCG1 mediate lipid removal are still unclear. Particularly, three questions remain controversial and are discussed in this review: (1) Do apoA-I and HDL directly interact with ABCA1 and ABCG1, respectively? (2) Does cholesterol efflux involve retroendocytosis of apoA-I or HDL? (3) Which lipids are directly transported by ABCA1 and ABCG1?
Cavelier
Clara
C
Institute of Clinical Chemistry, University Hospital Zurich, University Zurich, Rämistrasse 100, CH 8091 Zurich, Switzerland.
Lorenzi
Iris
I
Rohrer
Lucia
L
von Eckardstein
Arnold
A
D064286:ATP Binding Cassette Transporter 1; D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism; D001692:Biological Transport; D002318:Cardiovascular Diseases / Q000209:etiology / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D004705:Endocytosis; D006801:Humans; D008055:Lipids; D008075:Lipoproteins, HDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D011485:Protein Binding
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; D008055:Lipids; D008075:Lipoproteins, HDL; D002784:Cholesterol