HEK293 cells transfected with ABCG2-K86M display no transport activity. HEK293 cells transfected with ABCG2-K86M display no transport activity. The cells were incubated for 30 minutes at 37°C (accumulation) with 100 nM BODIPY-prazosin in the presence or absence of the specific ABCG2 inhibitor Fumitremorgin C (FTC) (5 μM). The cells were washed and incubated with or without 5 μM FTC for 60 minutes at 37°C (efflux). The histograms show intracellular fluorescence after accumulation and efflux of BODIPY-prazosin (100 nM) in the presence (broken line) or absence (unbroken line) of 5 μM FTC. Fluorescence was measured (FL-1) after excitation with a 488 nm argon laser. Ulla Henriksen et al. J Cell Sci 2005;118:1417-1426 © The Company of Biologists Limited 2005