Preparation of pure tyrosinated or detyrosinated tubulin isoforms

Post-translational modifications of tubulin: pathways to functional diversity of microtubules

Tubulin and microtubules are subject to a remarkable number of post-translational modifications. Understanding the roles these modifications play in determining the functions and properties of microtubules has presented a major challenge that is only now being met. Many of these modifications are found concurrently, leading to considerable diversity in cellular microtubules, which varies with development, differentiation, cell compartment, and cell cycle. We now know that post-translational modifications of tubulin affect, not only the dynamics of the microtubules, but also their organization and interaction with other cellular components. Many early suggestions of how post-translational modifications affect microtubules have been replaced with new ideas and even new modifications as our understanding of cellular microtubule diversity comes into focus.

Non-centrosomal microtubules regulate F-actin organization through the suppression of GEF-H1 activity

Animal cells contain two populations of microtubules: one radiating from the centrosome and the other growing from non-centrosomal sites. Whether or not they have differing roles in cellular architecture and function remains not fully understood. The cytoplasmic protein Nezha (also known as CAMSAP3) stabilizes non-centrosomal microtubules by attaching to their minus ends. Here, we found that depletion of CAMSAP3 in HeLa cells resulted in a relative increase in centrosomal microtubules, and this change was accompanied by accelerated actin stress fiber formation. In these cells, RhoA activity was upregulated, and the soluble fraction of GEF-H1, a RhoGEF whose activity is inhibited by binding to microtubules, increased, explaining why stress fiber formation was promoted. We further found that CAMSAP3 depletion led to an increase in detyrosinated microtubules, and these microtubules did not interact with GEF-H1. These findings suggest that CAMSAP3-anchored non-centrosomal microtubules capture GEF-H1 more efficiently than other microtubules do and that a balance between these microtubules is important to maintain proper actin organization.