Intracellular trafficking of recycling apolipoprotein E in Chinese hamster ovary cells

J Lipid Res. 2006 Jun;47(6):1176-86. doi: 10.1194/jlr.M500503-JLR200. Epub 2006 Mar 13.

Abstract

We have investigated apolipoprotein E (apoE) recycling in Chinese hamster ovary (CHO) cells, a peripheral cell that does not produce lipoproteins or express apoE. Using a pulse-chase protocol in which cells were pulsed with 125I-apoE-VLDL and chased for different periods, approximately 30% of the apoE internalized during the pulse was resecreted within a 4 h chase in a relatively lipid-free state. The addition of lysosomotropic agents or brefeldin A had no effect on apoE recycling. Unlike previous results with hepatocytes and macrophages, neither apoA-I nor upregulation of ABCA1 stimulated apoE recycling. However, cyclodextrin, which extracts cholesterol from plasma membrane lipid rafts, increased recycling. Confocal studies revealed that apoE, internalized during a 1 h pulse, colocalizes with early endosomal antigen-1, Rab5, Rab11a, and lysobisphosphatidic acid but not with lysosomal-associated membrane protein-1. Colocalization of apoE and Rab11a persisted even after cells had been chased for 1 h, suggesting a pool of apoE within the endosomal recycling compartment (ERC). Our data suggest that apoE recycling in CHO cells is linked to cellular cholesterol removal via the ERC and phospholipid-containing acceptors in a pathway alternative to the ABCA1-apoA-I axis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters / metabolism
  • ATP-Binding Cassette Transporters / physiology
  • Animals
  • Apolipoprotein A-I / metabolism
  • Apolipoprotein A-I / physiology
  • Apolipoproteins E / metabolism*
  • Brefeldin A / pharmacology
  • CHO Cells
  • Chloroquine / pharmacology
  • Cholesterol / metabolism
  • Cricetinae
  • Cricetulus
  • Cyclodextrins / pharmacology
  • Female
  • Fluorescent Antibody Technique
  • Humans
  • Lipoproteins, VLDL / metabolism*
  • Microscopy, Confocal
  • Monensin / pharmacology
  • Protein Transport / drug effects

Substances

  • ABCA1 protein, human
  • ATP Binding Cassette Transporter 1
  • ATP-Binding Cassette Transporters
  • Apolipoprotein A-I
  • Apolipoproteins E
  • Cyclodextrins
  • Lipoproteins, VLDL
  • Brefeldin A
  • Chloroquine
  • Monensin
  • Cholesterol