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. 1981 Dec;78(12):7545–7549. doi: 10.1073/pnas.78.12.7545

Mouse macrophages synthesize and secrete a protein resembling apolipoprotein E.

S K Basu, M S Brown, Y K Ho, R J Havel, J L Goldstein
PMCID: PMC349305  PMID: 6950395

Abstract

Monolayers of mouse peritoneal macrophages were shown to synthesize and secrete a protein that resembles apoprotein E (apoE), a normal constituent of plasma lipoproteins. Synthesis and secretion were studied by incubation of macrophages with L-[35S]methionine and analysis of the 35S-labeled proteins secreted into the culture medium. The 35S-labeled protein resembling apoE showed the following properties: (i) it floated in the ultracentrifuge at a density less than 1.215 g/ml, indicating that it was associated with lipid; (ii) by NaDodSO4/polyacrylamide gel electrophoresis, its Mr of 35,000 was identical to that of authentic apoE obtained from mouse plasma very low density lipoprotein; (iii) its isoelectric point of 5.4 was the same as that of authentic mouse apoE; (iv) it comigrated with authentic mouse apoE after two-dimensional isoelectric focusing/NaDodSO4/polyacrylamide gel electrophoresis; and (v) it was quantitatively precipitated by a monospecific antibody directed against rat apoE. Synthesis and secretion of the apoE-like protein was stimulated 3- to 8-fold when the macrophages were loaded with cholesterol by incubation with either acetylated low density lipoprotein (acetyl-LDL) or beta-migrating very low density lipoprotein from cholesterol-fed rabbits. When the cells were incubated with acetyl-LDL, the apoE-like protein composed approximately 2% of the total 35S-labeled protein synthesized by the cells and approximately 10% of the total 35S-labeled protein secreted into the medium. The current findings suggest a role for apoE in the plasma transport of cholesterol excreted from cholesterol-loaded macrophages.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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