Fig. 1.

Transient expression and dye extrusion capacities of WT and mutant ABCG2 forms in HEK cells 48 h after transfection. a Western blot of transfected HEK cells. (Left panel: representative Western-blot, right panel: densitometry results of four blots.) The R147W and R383C variants showed no measurable expression, and the K86M, M71V and Q141K variants showed significantly reduced expression. The T153M and F373C variants showed slightly lower expression than WT, while K360Δ, T434M and S476P were similar to WT. b Determination of cell surface expression of ABCG2 by 5D3 antibody labelling. We could not detect surface expression in the case of the R147W and R383C variants; M71V and F373C showed significantly lower cell surface expression than WT (four independent parallel experiments). c Measurement of Hoechst dye extrusion capacity. In case of the R147W and R383C variants we could measure similar, very low MDR activity factors than in the case of the non-functional mutant K86M, and the IRES-empty vectors. The Q141K, K360Δ T434M and S476P proteins showed somewhat lower activities than the WT ABCG2 (four independent parallel experiments). d Confocal images of HEK cells transiently expressing the ABCG2 variants. The variants which could be expressed all reached the plasma membrane. The scale bars represent 20 μm. Blue: DAPI, red: ABCG2. The stars indicate the results of t-tests; *p < 0.05, **p < 0.01, ***p < 0.001