CHOLESTEROL EFFLUX, CHOLESTEROL ESTERIFICATION, AND CHOLESTERYL ESTERTRANSFER BY LPA-I AND LPA-I A-II IN NATIVE PLASMA/

HDLs encompass structurally heterogeneous particles that fulfill speci fic functions in reverse cholesterol transport. Two-dimensional nonden aturing polyacrylamide gradient gel electrophoresis (2D-PAGGE) of norm al plasma and subsequent immunoblotting with anti-apolipoprotein (ape) A-I antibodies differentiates an abundant particle with electrophoret ic alpha-mobility and less abundant particles with electrophoretic pre -beta-mobility (pre beta(1)-LpA-I, pre beta(2)-LpA-I, pre beta(3)LpA-I ). Immunodetection with anti-apoA-II antibodies identifies a single pa rticle with alpha-mobility. To differentiate alpha-migrating HDL witho ut apo A-II (alpha-LpA-I) from those with apoA-II (alpha-LpA-I/A-II), we combined 2D-PAGGE with immunoadsorption of apoA-II. Incubation of p lasma with [H-3]cholesterol-labeled fibroblasts in combination with im munosubtracting 2D-PAGGE allowed us to analyze the role of alpha-LpA-I and alpha-LpA-I/A-II in the uptake and esterification of cell-derived cholesterol in native plasma. Depending on the duration of incubation s with cells, alpha-LpA-I took up two to four times more [H-3]-cholest erol than alpha-LpA-I/A-II. Irrespective of the duration of incubation , two to three times more [H-3]cholesteryl esters accumulated in alpha -LpA-I than in alpha-LpA-I/A-II. Subsequent incubations in the presenc e of an inhibitor of lecithin:cholesterol acyltransferase led to prefe rential accumulation of [H-3]cholesteryl esters in alpha-LpA-I/A-II. I n conclusion, our data indicate that alpha-LpA-I is more effective tha n alpha-LpA-I/A-II in both uptake and esterification of cell-derived c holesterol. Moreover, alpha-LpA-I/A-II appears to accumulate cholester yl esters, at least partially, from alpha-LpA-I.