Intracellular trafficking of recycling apolipoprotein E in Chinese hamster ovary cells.

Braun NA, Mohler PJ, Weisgraber KH, Hasty AH, Linton MF, Yancey PG, Su YR, Fazio S, Swift LL
J Lipid Res. 2006 47 (6): 1176-86

PMID: 16534141 · DOI:10.1194/jlr.M500503-JLR200

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.

MeSH Terms (19)

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

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