Figure 6.

LAMP1-positive storage vesicles express GM130 and sec23COPII in MPSIIIB mouse neuron cultures. Wild-type or MPSIIIB cortical neurons cultures were fixed at day 11 and immunolabeled for LAMP1 (in purple), GM130 (in green), and sec23-COPII (in red in A and B, in green in C). Nuclei were counterstained in blue. A: Low-magnification confocal immunofluorescence views show vesicles triply positive for LAMP1, GM130, and COPII (arrows) in MPSIIIB neurites. Scale bars, 10 μm. B: Areas boxed in the low magnification view of a MPSIIIB neuron (upper row) were examined at high magnification. Middle row shows a cluster of distended vesicles costained with the three antibodies. Bottom row shows images consistent with the incorporation of a GM130-positive vesicle in a LAMP1-COPII-positive vesicular complex (arrowhead). Scale bars, 10 μm in upper row; 1 μm in middle and bottom rows. C: A low magnification confocal image of a MPSIIIB neuron costained with LAMP1 and COPII antibodies is shown on the left. A high-magnification deconvoluted image of the boxed area is shown in the middle. Contiguous staining for LAMP1 and COPII is visible in vesicle limiting membranes. Three-dimensional views of the vesicle in the upper right corner are shown in the right panels, without (top) or with (bottom) isosurface treatment. Scale bars, 10 μm in left image; 1 μm in middle image.