Lipoproteins containing apolipoprotein A-IV but not apolipoprotein A-I take up and esterify cell-derived cholesterol in plasma.
Two-dimensional nondenaturing polyacrylamide gradient gel electrophoresis (2D-PAGGE) identifies distinct apoA-I-or apoE-containing subclasses of high-density lipoproteins (HDLs), each of which plays a different role in reverse cholesterol transport. In this study we used 2D-PAGGE to investigate the role of apoA-IV-containing lipoproteins in reverse cholesterol transport in native plasma. Incubation of 2D electrophoretograms with anti-apoA-IV antibodies identified up to three subclasses of particles. The smaller particle subclasses, LpA-IV-1 and LpA-IV-2, were found in every plasma sample. The largest particle subclass, LpA-IV-3, was observed in fewer than 10% of the plasmas analyzed. 2D-PAGGE of apoA-I-deficient plasma and apoA-I-depleted plasma and anti-apoA-I immunosubtracting 2D-PAGGE of normal plasma revealed that LpA-IV-1 and LpA-IV-2 do not contain apoA-I. The importance of LpA-IV-1 and LpA-IV-2 for uptake and esterification of cell-derived cholesterol was investigated using pulse-chase incubations of plasma with [3H]cholesterol-labeled fibroblasts followed by anti-apoA-I immunosubtracting 2D-PAGGE. During 1-minute pulse incubation with cells, [3H]cholesterol was taken up by gamma-LpE > LpA-IV-1 > pre-beta 1-LpA-I > LpA-IV-2 (">" denotes "more than"). During subsequent chase incubation without cells, proportionately less radioactivity disappeared from LpA-IV-1 and LpA-IV-2 than from pre-beta 1-LpA-I and gamma-LpE. During 5-minute pulse incubations, radioactive cholesteryl esters were formed in pre-beta 3-LpA-I > alpha-LpA-I > LpA-IV-1 > LpA-IV-2. The fractional estertification rate was highest in pre-beta 2-LpA-I and lowest in alpha-LpA-I.(ABSTRACT TRUNCATED AT 250 WORDS)
von Eckardstein
A
A
Institut für Klinische Chemie und Laboratoriumsmedizin, Zentrallaboratorium. Westfälische Wilhelms-Universität Münster, FRG.
Huang
Y
Y
Wu
S
S
Sarmadi
A S
AS
Schwarz
S
S
Steinmetz
A
A
Assmann
G
G
D016632:Apolipoprotein A-I / Q000378:metabolism*; D001692:Biological Transport; D002478:Cells, Cultured; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004951:Esterification; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans
D016632:Apolipoprotein A-I; D002784:Cholesterol