Stimulation of LDL receptor activity in Hep-G2 cells by a serum factor(s)

Journal Article · Sun May 01 04:00:00 EDT 1988 · J. Cell. Physiol.; (United States)

DOI:https://doi.org/10.1002/jcp.1041350208· OSTI ID:6859875

Ellsworth, J L; Brown, C; Cooper, A D

The regulation of low-density lipoprotein (LDL) receptor activity in the human hepatoma cell line Hep-G2 by serum components was examined. Incubation of dense monolayers of Hep-G2 cells with fresh medium containing 10% fetal calf serum (FM) produced a time-dependent increase in LDL receptor activity. Uptake and degradation of 125I-LDL was stimulated two- to four-fold, as compared with that of Hep-G2 cells cultured in the same media in which they had been grown to confluence (CM); the maximal 125I-LDL uptake plus degradation increased from 0.2 microgram/mg cell protein/4 h to 0.8 microgram/mg cell protein/4 h. In addition, a two-fold increase in cell surface binding of 125I-LDL to Hep-G2 cells was observed when binding was measured at 4 degrees C. There was no change in the apparent Kd. The stimulation of LDL receptor activity was suppressed in a concentration-dependent manner by the addition of cholesterol, as LDL, to the cell medium. In contrast to the stimulation of LDL receptor activity, FM did not affect the uptake or degradation of 125I-asialoorosomucoid. Addition of FM increased the protein content per dish, and DNA synthesis was stimulated approximately five-fold, as measured by (3H)thymidine incorporation into DNA; however, the cell number did not change. Cellular cholesterol biosynthesis was also stimulated by FM; (14C)acetate incorporation into unesterified and esterified cholesterol was increased approximately five-fold. Incubation of Hep-G2 cells with high-density lipoproteins (200 micrograms protein/ml) or albumin (8.0 mg/ml) in the absence of the serum factor did not significantly increase the total processed 125I-LDL. Stimulation of LDL receptor activity was dependent on a heat-stable, nondialyzable serum component that eluted in the inclusion volume of a Sephadex G-75 column.

• Research Organization: Stanford Univ. School of Medicine, CA (USA)
• OSTI ID: 6859875
• Journal Information: J. Cell. Physiol.; (United States), Journal Name: J. Cell. Physiol.; (United States) Vol. 135:2; ISSN JCLLA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETATES
ANIMAL CELLS
ANIMALS
AZINES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BLOOD SERUM
CARBON 14 COMPOUNDS
CARBOXYLIC ACID SALTS
CHOLESTEROL
CULTURE MEDIA
DAYS LIVING RADIOISOTOPES
DISEASES
DNA REPLICATION
DOSE-RESPONSE RELATIONSHIPS
ELECTRON CAPTURE RADIOISOTOPES
GROWTH FACTORS
HEPATOMAS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIPIDS
LIPOPROTEINS
MAMMALS
MAN
MEMBRANE PROTEINS
MITOGENS
NEOPLASMS
NUCLEI
NUCLEIC ACID REPLICATION
NUCLEOSIDES
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PRIMATES
PROTEINS
PYRIMIDINES
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RESPONSE MODIFYING FACTORS
RIBOSIDES
STEROIDS
STEROLS
THYMIDINE
TIME DEPENDENCE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TUMOR CELLS
VERTEBRATES