Abstract
Major microtubules in epithelial cells are not anchored to the centrosome, in contrast to the centrosomal radiation of microtubules in other cell types. It remains to be discovered how these epithelial microtubules are generated and stabilized at noncentrosomal sites. Here, we found that Nezha [also known as calmodulin-regulated spectrin-associated protein 3 (CAMSAP3)] and its related protein, CAMSAP2, cooperate in organization of noncentrosomal microtubules. These two CAMSAP molecules coclustered at the minus ends of noncentrosomal microtubules and thereby stabilized them. Depletion of CAMSAPs caused a marked reduction of microtubules with polymerizing plus ends, concomitantly inducing the growth of microtubules from the centrosome. In CAMSAP-depleted cells, early endosomes and the Golgi apparatus exhibited irregular distributions. These effects of CAMSAP depletion were maximized when both CAMSAPs were removed. These findings suggest that CAMSAP2 and -3 work together to maintain noncentrosomal microtubules, suppressing the microtubule-organizing ability of the centrosome, and that the network of CAMSAP-anchored microtubules is important for proper organelle assembly.