Figure 4.

Silencing of SNAPIN in human macrophages did not affect fusion of late endosomes with lysosomes. Macrophages were transfected with NS (A) or SNAPIN siRNAs (B) and then examined by immunofluorescence microscopy employing antibodies to LAMP1 (green) and RAB7 (red). Both molecules exhibited perinuclear localization, however, colocalization was not apparent (left panel). The area marked in panel (B), was expanded in panel (C). Following SNAPIN siRNA transfection, a portion of the LAMP1-positive lysosomes incorporated RAB7 (arrow). (D) Human primary macrophages transfected with siRNAs were incubated with Alexa Fluor 488 dextran (green) for 2 h, chased for 16 h and stained with LAMP1. Swollen LAMP1-positive lysosomes containing dextran are marked by arrows. (E) Enlarged area indicated in panel (D). Scale bar: 13.3 μm. The images were processed by deconvolution with NIS-element imaging software. Results in this figure are representative of 3 independent experiments.