Fig. 6

Cell surface antibody binding enhances rapid transport of APP to the lysosome but not to the early endosome. a SN56 cells were transfected with βAPP-CFP (not shown) and either LAMP1-mRFP or Rab5-mRFP or (red). APP was surface-labeled with FlAsH reagent (green) on ice for 3 min. No antibody labeling was used. Cells were either directly fixed (0 min) or incubated at 37 °C for 15 min and then fixed. Co-localized green/red pixels are overlayed in white. Each image shows a single cell, with approximate outline superimposed for clarity. In the absence of antibody, FlAsH labeled APP moves mostly to the early endosome. Approximate outlines of each cell is overlaid. Scale bar = 5 microns. b SN56 cells were transfected with HA-βAPP-CFP (not shown) and LAMP1-mRFP (red). APP was surface-labeled with FlAsH reagent (yellow) on ice for 3 min and then with 647-labeled anti-HA antibody (green) for 30 min on ice. After 15 min at 37 °C, both labels show extensive co-localization with lysosome. c Co-localized pixels were quantitated from the antibody crosslinking experiments in A and B in at least 10 cells from at least 3 experiments using an ANOVA with Tukey post-test. * denotes p < 0.05. Scale bar = 5 microns