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Published online 5 March 2001. doi:10.1083/jcb.152.5.1071
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© The Rockefeller University Press, 0021-9525/2001//1071 $5.00
The Journal of Cell Biology, Volume 152, Number 5, , 2001 1071-1078

Original Article

Accumulation of Caveolin in the Endoplasmic Reticulum Redirects the Protein to Lipid Storage Droplets



Anne G. Ostermeyera, James M. Pacia, Youchun Zengb, Douglas M. Lublinb, Sean Munroc, and Deborah A. Browna

a Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, Stony Brook, New York 11794
b Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110
c Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
Department of Biochemistry and Cell Biology, SUNY at Stony Brook, Stony Brook, NY 11794-5215.631-632-8575631-632-8563

deborah.brown{at}sunysb.edu

Caveolin-1 is normally localized in plasma membrane caveolae and the Golgi apparatus in mammalian cells. We found three treatments that redirected the protein to lipid storage droplets, identified by staining with the lipophilic dye Nile red and the marker protein ADRP. Caveolin-1 was targeted to the droplets when linked to the ER-retrieval sequence, KKSL, generating Cav–KKSL. Cav–{Delta}N2, an internal deletion mutant, also accumulated in the droplets, as well as in a Golgi-like structure. Third, incubation of cells with brefeldin A caused caveolin-1 to accumulate in the droplets. This localization persisted after drug washout, showing that caveolin-1 was transported out of the droplets slowly or not at all. Some overexpressed caveolin-2 was also present in lipid droplets. Experimental reduction of cellular cholesteryl ester by 80% did not prevent targeting of Cav–KKSL to the droplets. Cav–KKSL expression did not grossly alter cellular triacylglyceride or cholesteryl levels, although droplet morphology was affected in some cells. These data suggest that accumulation of caveolin-1 to unusually high levels in the ER causes targeting to lipid droplets, and that mechanisms must exist to ensure the rapid exit of newly synthesized caveolin-1 from the ER to avoid this fate.

Key Words: caveolae • brefeldin A • retrograde transport • triacylglycerol • cholesteryl ester

© 2001 The Rockefeller University Press

Abbreviations used in this paper: ACAT, acyl CoA:cholesterol acyl transferase; ADRP, adipocyte differentiation related protein; BFA, brefeldin A; CE, cholesteryl ester; DTAF, dichlorotriazinylaminofluorescein; FRT, Fischer rat thyroid; IF, immunofluorescence; LPDS, lipoprotein-depleted serum; TG, triacylglyceride.


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