The recycling of apolipoprotein E in macrophages: Influence of HDL and apolipoprotein A-I

Alyssa H. Hasty, Michelle R. Plummer, Karl H. Weisgraber, MacRae F. Linton, Sergio Fazio, Larry L. Swift

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

The ability of apolipoprotein E (apoE) to be spared degradation in lysosomes and to recycle to the cell surface has been demonstrated by our group and others, but its physiologic relevance is unknown. In this study, we characterized apoE recycling in primary murine macrophages and probed the effects of HDL and apoA-I on this process. In cells pulsed with 125I•apoE bound to VLDL, intact apoE was found in the chase medium for up to 24 h after the pulse. Approximately 27 ± 5% of the apoE internalized during the pulse was recycled after 4 h of chase. Addition of apoA-I and HDL increased apoE recycling to 45 ± 3% and 46 ± 3%, respectively, similar to the amount of apoE recycled after pulsing the cells with 125I•apoE•HDL. In addition, apoA-I-producing macrophages from transgenic mice showed increased apoE recycling at 4 h (38 ± 3%). Increased ABCA1 expression potentiated apoE recycling, suggesting that recycling occurs via ABCA1. Finally, in the presence of apoA-I, recycled apoE exited the cells on HDL-like particles. These results suggest that apoE recycling in macrophages may be part of a larger signaling loop activated by HDL and directed at maximizing cholesterol losses from the cell.

Original languageEnglish (US)
Pages (from-to)1433-1439
Number of pages7
JournalJournal of lipid research
Volume46
Issue number7
DOIs
StatePublished - 2005
Externally publishedYes

Keywords

  • Apolipoprotein E
  • Atherosclerosis
  • Cholesterol
  • Efflux
  • High density lipoprotein
  • Macrophage

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

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