Microtubule minus-end stabilization by polymerization-driven CAMSAP deposition.

Microtubules are cytoskeletal polymers with two structurally and functionally distinct ends, the plus- and the minus-end. Here, we focus on the mechanisms underlying the regulation of microtubule minus-ends by the CAMSAP/Nezha/Patronin protein family. We show that CAMSAP2 is required for the proper organization and stabilization of interphase microtubules and directional cell migration. By combining live-cell imaging and in vitro reconstitution of microtubule assembly from purified components with laser microsurgery, we demonstrate that CAMSAPs regulate microtubule minus-end growth and are specifically deposited on the lattice formed by microtubule minus-end polymerization. This process leads to the formation of CAMSAP-decorated microtubule stretches, which are stabilized from both ends and serve as sites of noncentrosomal microtubule outgrowth. The length of the stretches is regulated by the microtubule-severing protein katanin, which interacts with CAMSAPs. Our data thus indicate that microtubule minus-end assembly drives the stabilization of noncentrosomal microtubules and that katanin regulates this process.