Function of MRP1 is not dependent on cholesterol or cholesterol-stabilized lipid rafts

Peter Meszaros , Karin Klappe , Ina Hummel , Dick Hoekstra , Jan Willem Kok (1)

1 Cell Biology

MRP1 ‡ has been localized in cholesterol-enriched lipid rafts, which suggests a role for these lipid rafts and/or cholesterol in MRP1 function. Here we show for the first time that nearly complete oxidation of free cholesterol in the plasma membrane of BHK-MRP1 cells did not affect MRP1 localization in lipid rafts or its efflux function, using 5-carboxyfluorescein diacetate as substrate. Inhibition of cholesterol biosynthesis, using lovastatin in combination with RO 48-8071, resulted in a shift of Mrp1 out of lipid raft fractions, but did not affect Mrp1-mediated efflux in Neuro-2a cells. Short-term methyl-β-cyclodextrin treatment was equally effective in removing free cholesterol from Neuro-2a and BHK-MRP1 cells, but affected MRP1 function only in the latter. The kinetics of loss of both MRP1/Mrp1 efflux function and lipid raft association during long-term methyl-β-cyclodextrin treatment did not match the kinetics of free cholesterol removal in both cell lines. Moreover, MRP1 activity was measured in vesicles consisting of membranes isolated from BHK-MRP1 cells using the substrate cysteinyl leukotriene C4 and was not changed when the free cholesterol level of these membranes was either decreased or increased. In conclusion, MRP1/Mrp1 activity is not correlated with the level of free cholesterol or with localization in cholesterol-dependent lipid rafts.

Mots clés: Life Sciences

Peter Meszaros, Karin Klappe, Ina Hummel, Dick Hoekstra, Jan Willem Kok. Function of MRP1 is not dependent on cholesterol or cholesterol-stabilized lipid rafts. Biochemical Journal, 2011, 437 (3), pp.483-491. ⟨10.1042/BJ20110427⟩. ⟨hal-00608394⟩