Figure 4.

Ran localizes with microtubule minus-ends. (A) HeLa cells treated with Taxol were stained with the rabbit serum 0013, and either with anti-Ran, or with anti-α-tubulin antibodies. In addition to the centrosome a cloud of dots was labeled using anti-Ran antibody. This labeling colocalized with rabbit serum 0013, which recognizes centrosomal AKAP450. Double staining with the rabbit serum 0013 and anti-α-tubulin antibodies revealed that the punctate staining was localized at one microtubule end. Bar, 10 μm. (B) Ran localization in isolated inner and outer pillar cells from organ of corti at day 6, when most of the microtubule minus-ends are concentrated at the noncentrosomal apical sites. a, schematic diagram of the microtubules organization in the inner and outer pillar cells with the centrosome in pink, microtubules in blue, apical sites in yellow, and the nuclei in green. b and c, projections of optical sections through the lateral length of an inner pillar cell (b) and an outer pillar cell (c) immunolabeled with the anti-Ran antibody. The phase contrast images (blue) have been superimposed on the fluorescent images. Ran was concentrated at centrosomes (arrowheads) and at apical sites (large arrows). Ran staining in the nucleus (small arrows) varied from very strong (b) to weak (c).