Retroendocytosis of high density lipoproteins by the human hepatoma cell line, HepG2

Journal Article · Sun Jul 01 04:00:00 EDT 1990 · Arteriosclerosis (Dallas); (USA)

DOI:https://doi.org/10.1161/01.ATV.10.4.582· OSTI ID:6643253

Kambouris, A M; Roach, P D; Calvert, G D; Nestel, P J ^[1]

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1. CSIRO, Division of Human Nutrition, Adelaide (Australia)

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.

• OSTI ID: 6643253
• Journal Information: Arteriosclerosis (Dallas); (USA), Journal Name: Arteriosclerosis (Dallas); (USA) Vol. 10:4; ISSN ARTRD; ISSN 0276-5047
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
550901 -- Pathology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETIC ACID
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BIOASSAY
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
CARBOXYLIC ACIDS
CHEMISTRY
CHOLESTEROL
DAYS LIVING RADIOISOTOPES
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
HEPATOMAS
HYDROLASES
HYDROXY COMPOUNDS
IMMUNOASSAY
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIPIDS
LIPOPROTEINS
MAMMALS
MAN
MEMBRANE PROTEINS
METABOLISM
MONOCARBOXYLIC ACIDS
NEOPLASMS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDE HYDROLASES
PRIMATES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
SECRETION
SERINE PROTEINASES
STEROIDS
STEROLS
TRACER TECHNIQUES
TRYPSIN
TUMOR CELLS
VERTEBRATES