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 apolipoproteins A-I and D that catalyzes the esterification and transfer of cell-derived cholesterol.
The distribution of apolipoprotein A-I, apolipoprotein D, lecithin:cholesterol acyltransferase, and cholesteryl ester transfer protein 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 protein. Pulse-chase experiments determined that label generated in this 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 degrees C), less than 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 esters derived from it through a preferred pathway involving several minor pre beta-migrating lipoproteins to alpha-migrating high density lipoprotein.
Francone
O L
OL
Cardiovascular Research Institute, University of California Medical Center, San Francisco 94143.
Gurakar
A
A
Fielding
C
C
D000911:Antibodies, Monoclonal / Q000276:immunology; D016632:Apolipoprotein A-I; D001053:Apolipoproteins / Q000502:physiology*; D001054:Apolipoproteins A / Q000502:physiology*; D053399:Apolipoproteins D; D015153:Blotting, Western; D002352:Carrier Proteins / Q000097:blood*; D002784:Cholesterol / Q000378:metabolism*; D053480:Cholesterol Ester Transfer Proteins; D015180:Electrophoresis, Gel, Two-Dimensional; D006023:Glycoproteins; D006801:Humans; D066298:In Vitro Techniques; D008075:Lipoproteins, HDL / Q000378:metabolism*; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000097:blood*
D000911:Antibodies, Monoclonal; D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D001054:Apolipoproteins A; D053399:Apolipoproteins D; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D006023:Glycoproteins; D008075:Lipoproteins, HDL; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase