Overexpression of caveolin-1 increases plasma membrane fluidity and reduces P-glycoprotein function in Hs578T/Dox.
Cholesterol is a key lipid in mediating the enzyme activity or signaling pathway of many proteins on the plasma membrane in mammalian cells. In this report, we demonstrate for the first time that after overexpressing caveolin-1, the plasma membrane cholesterol level was decreased by about 12% and 30% for doxorubicin-sensitive and doxorubicin-resistant Hs578T breast cancer cells, respectively. However, the total cholesterol level in both cell lines was increased by about 10%. By measuring fluorescence and flow cytometry using the fluorescence dyes 1,6-diphenyl-1,3,5-hexatriene and Merocyanine 540, we found that overexpressing caveolin-1 resulted in a similar increase in membrane fluidity and loosening of lipid packing density as cholesterol depletion by 1 mM methyl-beta-cyclodextrin (MbetaCD) or 2-hydroxypropyl-beta-cyclodextrin (HbetaCD). Moreover, we found that the transport activity of P-gp was significantly inhibited by 1 mM MbetaCD or HbetaCD, which is also similar to the inhibitory effect of caveolin-1 overexpression. Our data demonstrate for the first time that the reduction of the plasma membrane cholesterol level induced by overexpressing caveolin-1 may indirectly inhibit P-gp transport activity by increasing plasma membrane fluidity.
Cai
Chuanxi
C
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Zhu
Hua
H
Chen
Jianwen
J
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D051242:Caveolin 1; D022461:Caveolins / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D008560:Membrane Fluidity; D021381:Protein Transport; D011994:Recombinant Proteins / Q000096:biosynthesis
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D011994:Recombinant Proteins; D004317:Doxorubicin; D002784:Cholesterol