Supplemental Material

This article contains the following supporting material:

• Movie 1 - Rab1-containing IC elements form reticular structures.
  Z-stack animation of a series of confocal images (0.5 μm thickness) taken from a NGF-treated PC12 cell (see also Figs. 3 C and C’) showing the redistribution of Rab1-positive IC elements (arrows) to the proximal region of the neurite, where they establish an extensive tubular reticulum (brackets).

• Movie 2 - Dynamics of GFP-Rab1A in HeLa cells.
  The movie corresponds to frames 251-499 from a total film of 500 images, acquired every 0.7 s. The images were inverted so that the fluorescence appears dark.

• Movie 3 - Dynamics of a peripheral GFP-Rab1A-positive site.
  This film highlights the cell area shown in the first image. The fluorescence intensity of the site indicated by the white arrow oscillates over time (see Fig. 5C). The arrow turns red to indicate the periodic increases in fluorescence, and green to indicate homotypic fusion between two IC elements. Red arrowheads follow mobile structures leaving the site, coinciding with rapid drops in fluorescence intensity (Fig. 5C).

• Movie 4 - Dynamics of YFP-p58 in HeLa cells.
  The square indicates an area where occasional dynamic tubules appear, connecting large globular elements. Some of the globular elements are mobile, but many remain stationary over time (arrow). Fusions between the globular elements are also seen. The weak reticular signal propably corresponds to an ER-pool of YFP-p58. (Film acquisition: 3.6 frames/sec).

• Movie 5 - Movements of GFP-Rab1A-positive tubules to the cell cortex.
  The rectangle in the top right corner indicates the cortical region of the NRK cell, to which the narrow IC tubules move. Note also the relatively stationary tubular elements underlying the plasma membrane, and the formation of reticular structures within the rectangle (Film acquisition: 10 frames/sec). See also Figure 6.

• Movie 6 - Dynamics of GFP-Rab1A in NGF-treated (24 h) PC12 cells.
  The film, obtained by time-lapse confocal microscopy, consists of 500 images (frames 0-499), taken at 1.2 s intervals. Note the bidirectional movements of IC structures in the proximal (“neck”) regions of the neurites. See also Figure 7.