Synthesis and secretion of apolipoprotein E occur independently of synthesis and secretion of apolipoprotein B-containing lipoproteins in HepG2 cells

S. Fazio, Z. Yao, B. J. McCarthy, S. C. Rall

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

The synthesis and secretion of apolipoprotein (apo) E, a major protein component of very low density lipoproteins, were examined in the human hepatoma cell line HepG2 under metabolic conditions known to stimulate lipogenesis and the production of apoB-containing lipoproteins. When HepG2 cells were incubated in the presence of fetal bovine serum (5 or 10%) or canine chylomicron remnants (5 or 10 μg of protein), the secretion of triglycerides and cholesteryl esters of lipoproteins of d < 1.063 g/ml increased, as determined by the incorporation of [14C]acetate. Determination of the distribution of apoE among media lipoproteins by agarose column chromatography showed that the majority of secreted apoE was associated with large lipoproteins when cells were incubated with fetal bovine serum. However, immunoblot analysis of total media apoE revealed that incubating cells with or without the lipogenic factors had no effect on the amount of apoE secreted. Pulse-chase and continuous labeling experiments demonstrated that the synthesis and secretion of apoE did not vary under the different metabolic conditions, even though there was a 5-fold increase in apoB secretion in response to increased lipogenesis. Neither apoE nor apoB mRNA levels responded to the lipogenic stimuli. We conclude that the synthesis and secretion of apoE are independent of the production of apoB- containing lipoproteins in HepG2 cells.

Original languageEnglish (US)
Pages (from-to)6941-6945
Number of pages5
JournalJournal of Biological Chemistry
Volume267
Issue number10
StatePublished - 1992
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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