CAMSAP3 accumulates in the pericentrosomal area and accompanies microtubule release from the centrosome via katanin

Abstract

The epithelium has an apico-basal axis polarity that plays an important role in absorption, excretion and other physiological functions. In epithelial cells, a substantial number of non-centrosomal microtubules (MTs) are scattered in the cytoplasm with an apico-basal polarity and reorientate as epithelial cells perform different functions. Several previous studies have found that non-centrosomal MTs are nucleated at the centrosome, and then released and translocated elsewhere. However, the detailed process and molecular mechanism remain largely unknown. In this study, we found that Nezha, also called calmodulinregulated spectrin-associated protein 3 (CAMSAP3), a non-centrosomal MT minus-end protein, accumulates in the pericentrosomal area and accompanies the release of MTs from the centrosome; whereas depletion of CAMSAP3 prevented MT release and instead caused focusing of MTs at centrosomes. Further studies demonstrated that CAMSAP3 precisely coordinates with dynein and katanin to regulate the MT detachment process. In conclusion, our results indicate that CAMSAP3 is a key molecule for generation of non-centrosomal MTs.

Augmin accumulation on long-lived microtubules drives amplification and kinetochore-directed growth

“…Two such mechanisms have been described: MT severing by Katanin (McNally and Vale, 1993; McNally et al, 2006; Roll-Mecak and McNally, 2010) and Augmin-mediated nucleation on the lattices of preexisting MTs. Transfection of siRNAs targeting Katanin (Dong et al, 2017) did not affect the distribution of EB3-EGFP fluorescence (Fig. S2).…”

CAMSAP3 facilitates basal body polarity and the formation of the central pair of microtubules in motile cilia

“…It is of interest, therefore, that CAMSAP3 is located more than 500 nm away from the center of the basal bodies, that is, at the distal end of the transition zone. CAMSAP3 is also known to interact with the MT-severing protein katanin, mutations of which have been shown to cause central-pair defects in Tetrahymena (6,50,51). It is, therefore, tempting to speculate that the balance between the nucleation regulated by CAMSAP3 and the destruction regulated by katanin represents a critical nexus for the control of central-pair formation.…”

A release-and-capture mechanism generates an essential non-centrosomal microtubule array during tube budding

“…Within the placode, the reduction in apical-medial Patronin without overall loss of microtubules could be due to junctional Patronin now binding microtubules that were severed at centrosomes and require anchoring. Alternatively, as has been described in cells in culture, loss or reduction of Patronin/CAMSAPs can directly affect the ability of Katanin to sever microtubules 48 , and thus upon Patronin depletion more microtubules may remain attached to the nucleating centrosome. Supporting this, Patronin colocalises with a pool of Katanin in the secretory cells of the placode (Fig.…”