Free cholesterol (FC) has been reported to efflux from cells through caveolae, which are 50-100 nm plasma membrane pits. The 22 kDa protein caveolin-1 is concentrated in caveolae and is required for their formation. The HDL scavenger receptor BI (SR-BI), which stimulates both FC efflux and selective uptake of HDL-derived cholesteryl ester (CE), has been reported to be concentrated in caveolae, suggesting that this localization facilitates flux of FC and CE across the membrane. However, we found

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... that overexpression of caveolin-1 in Fischer rat thyroid (FRT) cells, which lack caveolin-1 and caveolae, or HEK 293 cells, which normally express very low levels of caveolin-1, did not affect FC efflux to HDL or liposomes. Transient expression of SR-B1 did not affect this result. Similarly, caveolin-1 expression did not affect selective uptake of CE from labeled HDL particles in FRT or HEK 293 cells transfected with SR-BI. We conclude that basal and SR-BI-stimulated FC efflux to HDL and liposomes and SR-BI -mediated selective uptake of HDL CE are not affected by caveolin-1 expression in HEK 293 or FRT cells. -Wang, L., M. A. Connelly, A. G. Ostermeyer, H-h. Chen, D. L. Williams, and D. A. Brown. Caveolin-1 does not affect SR-BI-mediated cholesterol efflux or selective uptake of cholesteryl ester in two cell lines. J. Lipid Res. 2003. 44: 807-815. Supplementary key words caveolae • cholesterol traffic • lipid raft • scavenger receptor BI • high density lipoprotein Abbreviations: CE, cholesteryl ester; DOPC, dioleoyl phosphatidylcholine; FC, free cholesterol; FRT, Fischer rat thyroid; RCT, reverse cholesterol transport; SR-BI, scavenger receptor BI.