DISTRIBUTION AND FUNCTIONS OF LECITHIN - CHOLESTEROL ACYLTRANSFERASE AND CHOLESTERYL ESTER TRANSFER PROTEIN IN PLASMA-LIPOPROTEINS - EVIDENCE FOR A FUNCTIONAL UNIT CONTAINING THESE ACTIVITIES TOGETHER WITH APOLIPOPROTEIN-A-I AND APOLIPOPROTEIN-D THAT CATALYZES THE ESTERIFICATION AND TRANSFER OF CELL-DERIVED CHOLESTEROL

  • 25 April 1989
    • journal article
    • research article
    • Vol. 264  (12) , 7066-7072
Abstract
The distribution of apolipoprotein A-I, apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protien in fasting normal human plasma was determined by two-dimensional electrophoresis followed by immunoblotting. The synthesis and transfer of labeled cholesteryl esters generated in plasma briefly incubated with [3H]cholesterol-labeled fibroblasts was followed in terms of the lipoprotein species containing these antigens. Following the early appearance of labeled free cholesterol in two pre.beta.-migrating apolipoprotein A-I species (Castro, G. R., and Fielding, C. J. (1988) Biochemistry 27, 25-29), labeled esters were first detected, after a 2-min delay, in a third pre.beta.-migrating species which also contained apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protien. Pulse-chase exteriments determined that label generated in thks fraction was the precursor of at least a major part of labeled cholesteryl esters in the bulk of .alpha.-migrating high density lipoprotein. Over the maximum time course of these experiments (15 min, 37.degree. C), < 10% of labeled cholesteryl esters were recovered in low or very low density lipoproteins separated by electrophoresis, immunoaffinity, or heparin-agarose chromatography. These data suggest channeling of cell-derived cholesterol and cholesteryl ester derived from it through a preferred pathway involving several minor pre.beta.-migrating lipoproteins to .alpha.-migrating high density lipoprotein.