Research Article
Lipidomics reveals that adiposomes store ether lipids and mediate phospholipid traffic1,s⃞

https://doi.org/10.1194/jlr.M600413-JLR200Get rights and content
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Lipid droplets are accumulations of neutral lipids surrounded by a monolayer of phospholipids and associated proteins. Recent proteomic analysis of isolated droplets suggests that they are part of a dynamic organelle system that is involved in membrane traffic as well as packaging and distributing lipids in the cell. To gain a better insight into the function of droplets, we used a combination of mass spectrometry and NMR spectroscopy to characterize the lipid composition of this compartment. In addition to cholesteryl esters and triacylglycerols with mixed fatty acid composition, we found that ∼10–20% of the neutral lipids were the ether lipid monoalk(en)yl diacylglycerol. Although lipid droplets contain only 1–2% phospholipids by weight, >160 molecular species were identified and quantified. Phosphatidylcholine (PC) was the most abundant class, followed by phosphatidylethanolamine (PE), phosphatidylinositol, and ether-linked phosphatidylcholine (ePC). Relative to total membrane, droplet phospholipids were enriched in lysoPE, lysoPC, and PC but deficient in sphingomyelin, phosphatidylserine, and phosphatidic acid. These results suggest that droplets play a central role in ether lipid metabolism and intracellular lipid traffic.

lipid droplet
membranes
phospholipid turnover

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Published, JLR Papers in Press, January 8, 2007.

1

These two groups contributed equally to the project (Group 1: Bartz, Li, Zehmer, Anderson, and Liu; Group 2: Venables, Roth, Welti, and Chapman).

s⃞

The online version of this article (available at http://www.jlr.org) contains supplemental data in the form of 3 tables and 4 figures.