title: Human apolipoprotein A-IV binds to apolipoprotein A-I/A-II receptor sites and promotes cholesterol efflux from adipose cells.
abstract: Cholesterol efflux was studied in cultured mouse adipose cells after preloading with low density lipoprotein cholesterol. Exposure to complexes containing human apolipoprotein A-IV and L-alpha-dimyristoylphosphatidylcholine (DMPC) as well as to human lipoprotein particles containing apolipoprotein A-IV but not apolipoprotein A-I and particles containing apolipoproteins A-IV and A-I showed that both artificial and native apolipoprotein A-IV-containing particles were able to promote cholesterol efflux at 37 degrees C as a function of time and concentration. The half-maximal concentration was found to be 0.3 X 10(-6) M for apolipoprotein A-IV.DMPC complexes. Binding experiments performed in intact cells at 4 degrees C with labeled apolipoprotein A-IV.DMPC complexes showed the existence of specific binding sites, with a Kd value of 0.32 x 10(-6) M and a maximal binding capacity of 223,000 sites/cell. By cross-competition experiments with labeled and unlabeled complexes containing apolipoprotein A-IV, A-I, or A-II, it appeared that all three apolipoproteins bind to the same cell-surface recognition sites. It is suggested that apolipoprotein A-IV, which is present in the interstitial fluid surrounding adipose cells in vivo at concentrations similar to those required in vitro for the promotion of cholesterol efflux, plays a critical role in cholesterol removal from peripheral cells.
authors.affiliation: SERLIA, Institut Pasteur, Lille, France.
authors.forename: A
authors.initials: A
authors.lastname: Steinmetz
authors.forename: R
authors.initials: R
authors.lastname: Barbaras
authors.forename: N
authors.initials: N
authors.lastname: Ghalim
authors.forename: V
authors.initials: V
authors.lastname: Clavey
authors.forename: J C
authors.initials: JC
authors.lastname: Fruchart
authors.forename: G
authors.initials: G
authors.lastname: Ailhaud
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D051379:Mice; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018110:Receptors, Lipoprotein
chemical_list: D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; D011956:Receptors, Cell Surface; D018110:Receptors, Lipoprotein; C064018:apolipoprotein A-I A-II receptor; C022205:apolipoprotein A-IV; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine