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A Plasma Lipoprotein Containing Only Apolipoprotein E and with γ Mobility on Electrophoresis Releases Cholesterol from Cells

Yadong Huang, Arnold von Eckardstein, Shili Wu, Nobuyo Maeda and Gerd Assmann
Proceedings of the National Academy of Sciences of the United States of America
Vol. 91, No. 5 (Mar. 1, 1994), pp. 1834-1838
Stable URL: http://www.jstor.org/stable/2364031
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
A Plasma Lipoprotein Containing Only Apolipoprotein E and with γ Mobility on Electrophoresis Releases Cholesterol from Cells
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Abstract

Previous studies have identified lipid-poor high density lipoproteins with electrophoretic pre-β-mobility as the initial acceptors of cell-derived cholesterol in human plasma. These lipoproteins contain apolipoprotein A-I (apoA-I) as their sole apolipoprotein. In the present study, incubation of human plasma with [3H]cholesterol-laden skin fibroblasts has led to the identification of another lipoprotein that serves as a potent initial acceptor of cell-derived cholesterol. This lipoprotein, which we term γ-LpE, exhibits γ mobility on agarose gel electrophoresis. As determined by nondenaturing PAGE and by electron microscopy, the size of the spherical particle ranges between 12 and 16 nm. SDS/PAGE and subsequent immunoblotting identified apoE as its sole apolipoprotein. Plasma from normal and apoA-I-deficient mice, but not from apoE-deficient mice, released [3H]cholesterol from fibroblasts into a γ-migrating lipoprotein. Cell culture media from hepatoma cells or mouse peritoneal macrophages, both of which contain apoE of cellular origin, also promoted efflux of [3H]cholesterol from fibroblasts into a γ-migrating fraction. This was not observed with cell culture medium from fibroblasts alone. In conclusion, our results strongly indicate the presence in human plasma of a lipoprotein containing only apoE, γ-LpE, which is secreted by peripheral cells and is a potent acceptor of cell-derived cholesterol.

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