Figure 3.

Lysosomes displaced to the cell periphery by expression of Arl8b are more alkaline. The lysosomes of HeLa cells were loaded with fluorescein-dextran, a ratiometric pH-sensitive dye. Cells were then either mock transfected or transfected with Arl8b-mCherry cDNA. Lysosomal pH was measured by ratiometric fluorescence microscopy as described in the Ratiometric fluorescence microscopy section in Materials and methods. (a) Representative images of control and Arl8b-expressing cells with fluorescein fluorescence ratios converted to pH (see calibration bar). Cells of interest are outlined with dashed lines. Bars, 10 µm. (b) Lysosomal pH was determined in control and Arl8b-expressing cells. Error bars represent SEM (n = 30 and 39 cells from at least nine independent experiments for control and Arl8b transfectants, respectively).