Multidrug resistance (MDR) is a major obstacle in cancer therapy. It results from different mechanisms; among them is P-glycoprotein (P-gp)–mediated drug efflux out of cells. The mechanism of action remains elusive. The membrane lipid surrounding of P-gp, especially cholesterol, has been postulated to play an important role. To determine the effect of cholesterol depletion on P-gp, Madin Darby canine kidney (MDCK) cells, transfected with the mdr1 gene (MDR1-MDCK cells), were treated with methyl-β-cyclodextrin (MβCD). The localization and function of P-gp were analyzed using confocal laser scanning microscopy. Treatment with 100 mM MβCD did not affect viability but altered the structural appearance of the cells and abolished efflux of rhodamine 123, a P-gp substrate. The MβCD treatment released P-gp from intact cells into the supernatant and reduced the amount of P-gp in total membrane preparations. The P-gp was shifted from the raft fractions (1% Triton X-100, 4° C) to higher density fractions in MβCD-treated cells. The amount of cholesterol was significantly decreased in the raft fractions. Treatment of cells with 1-phenyl-2-decanoylamino-3-morpholino-1-propanol, a glucosylceramide synthase inhibitor, also led to a shift of P-gp to higher density fractions. These results show that removal of cholesterol modulates the membrane lipid composition, changes the localization of P-gp, and results in loss of P-gp function.
How to translate text using browser tools
1 July 2005
EFFECT OF THE MODULATION OF THE MEMBRANE LIPID COMPOSITION ON THE LOCALIZATION AND FUNCTION OF P-GLYCOPROTEIN IN MDR1-MDCK CELLS
SARAH W. KAMAU,
STEFANIE D. KRÄMER,
MAJA GÜNTHERT,
HEIDI WUNDERLI-ALLENSPACH
ACCESS THE FULL ARTICLE
It is not available for individual sale.
This article is only available to subscribers.
It is not available for individual sale.
It is not available for individual sale.
In Vitro Cellular & Developmental Biology - Animal
Vol. 41 • No. 7
July 2005
Vol. 41 • No. 7
July 2005
cholesterol
glycosphingolipids
P-glycoprotein
rafts