Figure 3

MOR-1 surface localization varies with the phase of the cell cycle. (A) TF-1 cells were grown on poly-D-lysine coverslips and left nonpermeabilized. Cells were then stained with a fluorescently tagged amphipathic molecule that embeds within the lipid bilayer. The molecule embeds preferentially into regions of high lipid density, and therefore these regions are represented by high fluorescence. (B) TF-1 cells were grown on poly-D-lysine coverslips and then treated with aphidicolin (10 μg/ml) for 16 hours to induce arrest in S phase. Following treatment, cells were left nonpermeabilized and stained for MOR-1 and with DAPI (4',6-diamidino-2-phenylindole). MOR-1 puncta are located diffusely throughout the cell. All images were obtained at 40× with an Olympus IX81 deconvolution microscope. (C) TF-1 cells were left untreated or arrested in S phase and stained for MOR-1 as described above, then analyzed by flow cytometry. Analysis shows an increase in MOR-1 expression in S phase, as indicated by an increase in mean fluorescent intensity.