The multidrug transporter, P-glycoprotein, actively mediates cholesterol redistribution in the cell membrane

Abstract

P-glycoprotein (P-gp) is a plasma membrane ATP-binding cassette transporter, responsible for multidrug resistance in tumor cells. P-gp catalyzes the ATP hydrolysis-dependent efflux of numerous amphiphilic compounds of unrelated chemical structures. In the absence of any identified substrate, P-gp exhibits an apparently futile, basal ATPase activity. By using native membrane vesicles containing high amounts of P-gp, we show here that (i) this basal ATPase activity is tightly dependent on the presence of cholesterol in the membrane; (ii) the stimulation of P-gp ATPase activity by drugs transported by P-gp is higher in the absence than in the presence of cholesterol and, conversely, the stimulation of P-gp ATPase activity by cholesterol is higher in the absence than in the presence of known P-gp substrates; (iii) P-gp mediates the ATPdependent relocation of cholesterol from the cytosolic leaflet to the exoplasmic leaflet of the plasma membrane; and (iv) the decrease of the cholesterol dependence of P-gp ATPase activity induced by known P-gp substrates is correlated with the inhibition of the ATP-dependent cholesterol redistribution within the membrane. These data are highly evocative of a coupling between the basal ATPase activity of P-gp and its intramembrane cholesterolredistribution function, and they are fully consistent with the possibility that P-gp may actively translocate cholesterol in the membrane. Finally, this P-gp-mediated cholesterol redistribution in the cell membrane makes it likely that P-gp contributes in stabilizing the cholesterol-rich microdomains, rafts and caveolae, and that it is involved in the regulation of cholesterol trafficking in cells.

MDR1 in immunity: friend or foe?

“…29,30 Other studies showed that the preferential localization of MDR1 in the lipid rafts and caveolae, characterized as detergent resistant membranes (DRM), is required for its functionality. 31,32 Indeed, cholesterol depletion that disrupts lipid rafts, abolishes membrane MDR1 localization and is associated with reduced efflux capacities. 33,34 Hypoxia can also induce MDR1 expression through the Hypoxia Inducible Factor 1α (HIF-1α) that binds the promoter of ABCB1 and activates its transcription.…”

Evaluation of the Contribution of the ATP Binding Cassette Transporter, P-glycoprotein, to in Vivo Cholesterol Homeostasis

“…Mechanistic in vitro studies demonstrated that Pgp binds cholesterol 10 and that the association between cholesterol and Pgp impacted its drug efflux activity 8,11 . Furthermore, Pgp was proposed to be an ATP-dependent "flippase" of cholesterol, maintaining cholesterol on the extracellular leaflet of the membrane bilayer 12 . Non-specific Pgp inhibitors disrupt trafficking of cholesterol from the plasma membrane to the endoplasmic reticulum, reducing synthesis and esterification of cholesterol without direct inhibition of ACAT, the enzyme responsible for cholesterol esterification [13][14][15][16][17] .…”

Endocytosis of fluorescent cyclodextrins by intestinal Caco-2 cells and its role in paclitaxel drug delivery

“…However, 57 excess amount of hydrophilic cyclodextrin can decrease the 58 penetration of drugs . (Arima et al, 2004;66 Fenyvesi et al, 2008;Garrigues et al, 2002).…”