Document Detail


Retroendocytosis of high density lipoproteins by the human hepatoma cell line, HepG2.
MedLine Citation:
PMID:  2369367     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
When human HepG2 hepatoma cells were pulsed with 125I-labeled high density lipoproteins (HDL) and chased in fresh medium, up to 65% of the radioactivity released was precipitable with trichloroacetic acid. Cell-internalized 125I-HDL contributed to the release of acid-precipitable material; when cells were treated with trypsin before the chase to remove 125I-HDL bound to the outer cell membrane, 50% of the released material was still acid-precipitable. Characterization of the radioactive material resecreted by trypsinized cells revealed the presence of particles that were similar in size and density to mature HDL and contained intact apolipoproteins (apo) A-I and A-II. The release of internalized label occurred at 37 degrees C but not at 4 degrees C. Monensin, which inhibits endosomal recycling of receptors, decreased the binding of 125I-HDL to cells by 75%, inhibited the release of internalized radioactivity as acid-precipitable material by 80%, and increased the release of acid-soluble material by 90%. In contrast, the lysosomal inhibitor chloroquine increased the association of 125I-HDL to cells by 25%, inhibited the release of precipitable material by 10%, and inhibited the release of acid-soluble radioactivity by 80%. Pre-incubation with cholesterol caused a 50% increase in the specific binding, internalization, and resecretion of HDL label. Cholesterol affected the release of acid-precipitable label much more (+90%) than that of acid-soluble material (+20%). Taken together, these findings suggest that HepG2 cells can bind, internalize, and resecrete HDL by a retroendocytotic process. Furthermore, the results with cholesterol and monensin indicate that a regulated, recycling, receptor-like molecule is involved in the binding and intracellular routing of HDL.
Authors:
A M Kambouris; P D Roach; G D Calvert; P J Nestel
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Arteriosclerosis (Dallas, Tex.)     Volume:  10     ISSN:  0276-5047     ISO Abbreviation:  Arteriosclerosis     Publication Date:    1990 Jul-Aug
Date Detail:
Created Date:  1990-08-13     Completed Date:  1990-08-13     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  8401388     Medline TA:  Arteriosclerosis     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  582-90     Citation Subset:  IM    
Affiliation:
CSIRO, Division of Human Nutrition, Adelaide, SA, Australia.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cell Line
Chemical Precipitation
Humans
Iodine Radioisotopes / diagnostic use
Lipoproteins, HDL / metabolism*
Liver Neoplasms, Experimental / metabolism*
Monensin / pharmacology
Trichloroacetic Acid / pharmacology
Trypsin / pharmacology
Tumor Cells, Cultured / drug effects,  metabolism*
Chemical
Reg. No./Substance:
0/Iodine Radioisotopes; 0/Lipoproteins, HDL; 17090-79-8/Monensin; 76-03-9/Trichloroacetic Acid; EC 3.4.21.4/Trypsin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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