Caveolin-1 does not affect SR-BI-mediated cholesterol efflux or selective uptake of cholesteryl ester in two cell lines.
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 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
Libo
L
Department of Biochemistry and Cell Biology, SUNY at Stony Brook, NY 11794, USA.
Connelly
Margery A
MA
Ostermeyer
Anne G
AG
Chen
Hsu-hsin
HH
Williams
David L
DL
Brown
Deborah A
DA
D000818:Animals; D018955:CD36 Antigens / Q000502:physiology*; D021941:Caveolae / Q000737:chemistry; D051242:Caveolin 1; D022461:Caveolins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism*; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins; D051381:Rats; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D014162:Transfection
C495540:CAV1 protein, human; D018955:CD36 Antigens; C495537:Cav1 protein, rat; D051242:Caveolin 1; D022461:Caveolins; D002788:Cholesterol Esters; D008075:Lipoproteins, HDL; D008081:Liposomes; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C454739:Scarb1 protein, mouse; C495125:Scarb1 protein, rat; D051122:Scavenger Receptors, Class B; D002784:Cholesterol