GLTP Mediated Non-Vesicular GM1 Transport between Native Membranes
Figure 1
GLTP readily inserts GM1 into the extracellular leaflet of HepG2 cells.
(A) HepG2 cells were incubated at 37°C for 10 min in a 20 min pre-incubated Ringer solution containing 0.2 mg/ml GM1-DOPC (5∶95 mol%)-liposomes with 0, 5, or 25 µM GLTP. Then cells were washed, stained in the cold with fluorescently labeled CTX, fixed and imaged. Pictures were recorded with a confocal laser scanning microscope in the differential interference contrast (DIC) and the fluorescence channel. Images in the lower panels are shown at the same scaling leading to the impression that in control cells staining is missing. However, also in control cells staining was present in the periphery (see Fig. S2A). (B) CTX staining intensity at the cell periphery was quantified by linescan analysis (three pixel width). Values are given as means ± SEM (n = 3 - 4 independent experiments; 19 - 35 cells were analyzed for each experiment).