Fig. 4. Distribution of p25SS in the endocytic pathway. Cells were transfected with myc-p25SS and then incubated with rabbit anti-myc antibodies, as in Fig. 2B. Where indicated, rhodamine-labeled dextran was added to the incubation medium during the last 60 minutes of incubation. To label late endosomes, 5 µg/ml monoclonal anti-LBPA antibody (6C4) were co-endocytosed with anti-myc antibodies, to limit accessibility problems within late endosomes (a non-relevant control antibody does not accumulate intracellularly [not shown and (Kobayashi et al., 1998)]. At this low dose, 6C4 does not interfere with trafficking. Then, endocytosed antibodies were revealed as in Fig. 2B using appropriate secondary antibodies. The distribution of antibody-tagged p25SS was compared with that of endocytosed dextran or anti-LBPA antibodies, or to Lamp1 (using anti-Lamp1 antibodies), as indicated. The bottom row shows the distribution of endocytosed dextran and LBPA in untransfected control cells; the right column shows the merged images. Scale bars: 10 µm.

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