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Lipids partition caveolin-1 from ER membranes into lipid droplets: updating the model of lipid droplet biogenesis.

Authors
  • Robenek, Mirko J
  • Severs, Nicholas J
  • Schlattmann, Karin
  • Plenz, Gabriele
  • Zimmer, Klaus-Peter
  • Troyer, David
  • Robenek, Horst
Type
Published Article
Journal
The FASEB Journal
Publisher
Federation of American Society for Experimental Biology
Publication Date
May 01, 2004
Volume
18
Issue
7
Pages
866–868
Identifiers
PMID: 15001554
Source
Medline
License
Unknown

Abstract

Caveolin-1, a putative mediator of intracellular cholesterol transport, is generally assumed to be integrated into the cytoplasmic leaflets of all cellular membranes. Lipid droplets form by budding at the endoplasmic reticulum (ER), and caveolin-1 is thought to be transferred to the droplet surface along with the cytoplasmic leaflet of ER membranes and not to enter the droplet core. We explored how caveolin-1 accesses lipid droplets from the ER by localizing caveolin-1 in ER membranes and in lipid droplets in cultured smooth muscle cells using freeze-fracture immunocytochemistry. We detected caveolin-1 in endoplasmic leaflets of ER membranes but never in cytoplasmic leaflets. Caveolin-1 was also present in lipid droplet cores. These findings are incompatible with the current hypothesis of lipid droplet biogenesis. We suggest that the inherent high affinity of caveolin-1 for neutral lipids causes caveolin-1 molecules to be extracted from the endoplasmic leaflets of ER membranes and to be transferred into the droplet core by inundating lipids during droplet formation.

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