ApoA‐IV Is Secreted on Discrete HDL Particles by the Rat Hepatoma Cell Line McA‐RH7777 Transfected With ApoA‐IV cDNA
作者:
Zemin Yao,
Stephen Lauer,
David Sanan,
Sergio Fazio,
期刊:
Arteriosclerosis and Thrombosis: A Journal of Vascular Biology
(OVID Available online 1993)
卷期:
Volume 13,
issue 10
页码: 1476-1486
ISSN:1049-8834
年代: 1993
出版商: OVID
关键词: apoA-IV secretion;HDL
数据来源: OVID
摘要:
In the present study, the synthesis and secretion of transfected apolipoprotein (apo) A-IV was investigated in rat hepatoma McA-RH7777, a cell line that does not express apoA-IV raRNA or protein. An expression plasmid that contained the rat apoA-IV cDNA was transfected into the cells; five stable transformants were selected that harbor different copy numbers of the apo A-IV construct and secrete different amounts of apoA-IV. Gel filtration column chromatography and density gradient ultracentrifugation, combined with gel electrophoresis and electron microscopy techniques, demonstrated that (1) the secreted apoA-IV associated mainly with high-density lipoproteins (HDLs) and only a trace amount of apoA-IV was associated with very-low-density lipoproteins; (2) overexpression of apoA-IV resulted in an increased number of disk-shaped structures (thickness, =8.0 nm and diameter, =22 nm); and (3) the electrophoretic mobilities of the apoA-IV-containing particles differed from those of apoA-I-containing HDL. Expression of apoA-IV exerted no discernible effect on the density distribution or the secretion efficiency of apoB-100. Additionally, secretion of apoB-100 and apoA-IV exhibited opposite responses to serum: apoB-100 secretion was stimulated eightfold after addition of serum, whereas apoA-IV secretion was inhibited by 40%. These results suggest that synthesis of apoA-I V may lead to the formation of a subclass of HDL with a different metabolic fate than that of lipoproteins containing either apoA-I or apoB.
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