Evidence for extralysosomal hydrolysis of high‐density lipoprotein cholesteryl esters in rat hepatoma cells (Fu5AH): A model for delivery of high‐density lipoprotein cholesterol
Identifieur interne : 002F75 ( Main/Exploration ); précédent : 002F74; suivant : 002F76Evidence for extralysosomal hydrolysis of high‐density lipoprotein cholesteryl esters in rat hepatoma cells (Fu5AH): A model for delivery of high‐density lipoprotein cholesterol
Auteurs : John G. Delamatre [États-Unis] ; Robert M. Carter [États-Unis] ; Conrad A. Hornick [États-Unis]Source :
- Journal of Cellular Physiology [ 0021-9541 ] ; 1991-01.
Abstract
Rat hepatoma cells (Fu5AH) were studied as a model for the net delivery of apoE‐free high‐density lipoprotein (HDL) cholesterol to a cell. Incubating cells with HDL results in (1) a decrease in both media‐free cholesterol and cholesteryl ester concentration; (2) decreased cell sterol synthesis; and (3) increased cell cholesteryl ester synthesis. HDL cholesteryl ester uptake is increased when cells are incubated for 18 hr in cholesterol poor media. Coincubation of 3H‐cholesteryl ester‐labeled low‐density lipoprotein (LDL) with 50 μM chloroquine or 25 μM monensin results in a decrease in the cellular free cholesterol/cholesteryl ester (FC/CE) isotope ratio, indicating an inhibition in the conversion of cholesteryl ester to free cholesterol. In contrast, chloroquine and monensin do not alter the cellular FC/CE isotope ratio for 3H‐CE HDL. This evidence indicates that acidic lysosomal cholesteryl ester hydrolase does not account for the hydrolysis of HDL‐CE. Free cholesterol generated from 3H‐cholesteryl ester of both LDL and HDL is reesterified intracellularly. At higher HDL concentrations (above 50 μg/ml) HDL cholesteryl ester hydrolysis is sensitive to chloroquine. We propose that an extralysosomal pathway is operating in the metabolism of HDL cholesterol and that at higher HDL concentrations a lysosomal pathway may be functioning in addition to an extralysosomal pathway.
Url:
DOI: 10.1002/jcp.1041460104
Affiliations:
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Delamatre</name><affiliation wicri:level="2"><country xml:lang="fr">États-Unis</country><placeName><region type="state">Louisiane</region></placeName><wicri:cityArea>Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans</wicri:cityArea></affiliation><affiliation wicri:level="2"><country xml:lang="fr">États-Unis</country><placeName><region type="state">Louisiane</region></placeName><wicri:cityArea>Correspondence address: Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans</wicri:cityArea></affiliation></author><author><name sortKey="Carter, Robert M" sort="Carter, Robert M" uniqKey="Carter R" first="Robert M." last="Carter">Robert M. 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Hornick</name><affiliation wicri:level="2"><country xml:lang="fr">États-Unis</country><placeName><region type="state">Louisiane</region></placeName><wicri:cityArea>Department of Physiology, Division of Lipoprotein Metabolism and Pathophysiology, Louisiana State University Medical Center, New Orleans</wicri:cityArea></affiliation></author></analytic><monogr></monogr><series><title level="j" type="main">Journal of Cellular Physiology</title><title level="j" type="alt">JOURNAL OF CELLULAR PHYSIOLOGY</title><idno type="ISSN">0021-9541</idno><idno type="eISSN">1097-4652</idno><imprint><biblScope unit="vol">146</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="18">18</biblScope><biblScope unit="page" to="24">24</biblScope><biblScope unit="page-count">7</biblScope><publisher>Wiley Subscription Services, Inc., A Wiley Company</publisher><pubPlace>Hoboken</pubPlace><date type="published" when="1991-01">1991-01</date></imprint><idno type="ISSN">0021-9541</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0021-9541</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Rat hepatoma cells (Fu5AH) were studied as a model for the net delivery of apoE‐free high‐density lipoprotein (HDL) cholesterol to a cell. Incubating cells with HDL results in (1) a decrease in both media‐free cholesterol and cholesteryl ester concentration; (2) decreased cell sterol synthesis; and (3) increased cell cholesteryl ester synthesis. HDL cholesteryl ester uptake is increased when cells are incubated for 18 hr in cholesterol poor media. Coincubation of 3H‐cholesteryl ester‐labeled low‐density lipoprotein (LDL) with 50 μM chloroquine or 25 μM monensin results in a decrease in the cellular free cholesterol/cholesteryl ester (FC/CE) isotope ratio, indicating an inhibition in the conversion of cholesteryl ester to free cholesterol. In contrast, chloroquine and monensin do not alter the cellular FC/CE isotope ratio for 3H‐CE HDL. This evidence indicates that acidic lysosomal cholesteryl ester hydrolase does not account for the hydrolysis of HDL‐CE. Free cholesterol generated from 3H‐cholesteryl ester of both LDL and HDL is reesterified intracellularly. At higher HDL concentrations (above 50 μg/ml) HDL cholesteryl ester hydrolysis is sensitive to chloroquine. We propose that an extralysosomal pathway is operating in the metabolism of HDL cholesterol and that at higher HDL concentrations a lysosomal pathway may be functioning in addition to an extralysosomal pathway.</div></front></TEI><affiliations><list><country><li>États-Unis</li></country><region><li>Louisiane</li></region></list><tree><country name="États-Unis"><region name="Louisiane"><name sortKey="Delamatre, John G" sort="Delamatre, John G" uniqKey="Delamatre J" first="John G." last="Delamatre">John G. Delamatre</name></region><name sortKey="Carter, Robert M" sort="Carter, Robert M" uniqKey="Carter R" first="Robert M." last="Carter">Robert M. Carter</name><name sortKey="Delamatre, John G" sort="Delamatre, John G" uniqKey="Delamatre J" first="John G." last="Delamatre">John G. Delamatre</name><name sortKey="Hornick, Conrad A" sort="Hornick, Conrad A" uniqKey="Hornick C" first="Conrad A." last="Hornick">Conrad A. Hornick</name></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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