DepartmentMolecular Cell Biology
Publication date11-Aug-2015

Ai Johjima, Kentaro Noi, Shingo Nishikori, Hirotsugu Ogi, Masatoshi Esaki, Teru Ogura. Microtubule severing by katanin p60 AAA+ ATPase requires the C-terminal acidic tails of both α- and β-tubulins and basic amino acid residues in the AAA+ ring pore. J. Biol. Chem. 290: 11762-11770 (2015)

The microtubule (MT) network is highly dynamic and undergoes dramatic reorganizations during the cell cycle. Dimers of α- and β-tubulins rapidly polymerize to and depolymerize from the end of MT fibrils in an intrinsic GTP-dependent manner. MT severing by ATP-driven enzymes such as katanin and spastin contributes significantly to microtubule dynamics, and it has been shown that katanin p60, a AAA+ family protein, has ATPase and MT-severing activities. The mechanism of MT severing by katanin p60 is poorly understood, and the residues in katanin p60 and tubulins important for severing activity were therefore explored in this study. MT-severing activity, but not ATPase activity, was inhibited by mutations of the conserved aromatic residue and the flanking basic residues in the pore region of the katanin p60 hexameric ring. When the acidic residue-rich C-terminal unstructured segment of either α- or β-tubulin was removed, polymerized MTs were resistant to katanin p60 treatment. Interactions between katanin p60 and the mutant MTs, on the other hand, were unaffected. Taken together, these findings led us to propose that the interactions between the positively charged residues of katanin p60 and the acidic tails of both tubulins are essential for efficient severing of MTs (Figure).


Fig.  A proposed mechanism for MT-severing by katanin p60. We propose possible mechanisms for the requirement of the C-terminal tails of both tubulins for MT-severing by katanin p60. Katanin p60 tends to oligomerize, possibly hexamerize, on MTs. The pore loop of katanin p60 may coincidentally capture C-terminal segments of both α- and β-tubulins. The simultaneous pulling of both tails may generate mechanical tension in the tubulin dimer, thereby leading to destabilization of tubulin-tubulin contacts in the lattice. The resulting defective interaction may promote the release of the tubulin dimer from the MT.