Identification of katanin, an ATPase that severs and disassembles stable microtubules

FJ McNally, RD Vale - Cell, 1993 - cell.com
FJ McNally, RD Vale
Cell, 1993cell.com
Ewkaryotic cells rapidly reorganize their microtubule cytoskeleton during the cell cycle,
differentiation, and cell migration. In this study, we have purified a heterodimeric protein,
katanin, that severs and disassembles microtubules to tubulin dimers. The disassembled
tubulin can repolymerize, indicating that it is not irreversibly modified or denatured in the
reaction. Katanin is a microtubule-stimulated ATPase and requires ATP hydrolysis to sever
microtubules. Katanin represents a novel type of enzyme that utilizes energy from nucleotide …
Summary
Ewkaryotic cells rapidly reorganize their microtubule cytoskeleton during the cell cycle, differentiation, and cell migration. In this study, we have purified a heterodimeric protein, katanin, that severs and disassembles microtubules to tubulin dimers. The disassembled tubulin can repolymerize, indicating that it is not irreversibly modified or denatured in the reaction. Katanin is a microtubule-stimulated ATPase and requires ATP hydrolysis to sever microtubules. Katanin represents a novel type of enzyme that utilizes energy from nucleotide hydrolysis to break tubulin-tubulin bonds within a microtubule polymer, a process that may aid in disassembling complex microtubule arrays within cells.
Microtubules, 25 nm diameter polymers composed of a/3-tubulin dimers, are essential for a variety of functions in eukaryotic cells. During interphase, these cytoskeletal filaments are required for organizing large intracellular membrane compartments, such as the Golgi apparatus (Ho et al., 1990) and the endoplasmic reticulum (Terasaki et al., 1986), as well as for transporting small membrane carrier vesicles in the endocytotic and secretory pathways (Vale, 1987). During mitosis, microtubules are the primary constituents of the mitotic spindle and are needed for proper segregation of chromosomes and for specifying the position of the cleavage furrow (Rappaport, 1985). To carry out its activities in mitosis and interphase, the network of microtubule polymers must be organized appropriately within the cytoplasm. In most interphase cells, microtubules are nucleated from the centrosome, a microtubule-organizing center located adjacent to the nucleus, and extend outward toward the periphery of the cell. This arrangement of microtubules is not static, and the network can rapidly reorganize during cell or growth cone migration (Kupfer et al., 1982; Gundersen and Bulinski, 1988; Sabry et al., 1991), interaction of T killer cells with their target cells (Geiger et al., 1982), and epithelial (Bacallao et al., 1989) and neuronal (Baas et al., 1989) differentiation. Perhaps the most dramatic alteration in the microtubule array takes place at the G2-M transition in the cell cycle (eg, Kitanishi-Yumura and Fukui, 1987), when the interphase microtubule network is rapidly and completely disassembled, followed by the reassembly of microtubules into a new configuration, the mitotic spindle. What factors enable microtubule networks to reorganize in! such a dynamic manner? The polymerization properties of pure tubulin provide at least a partial explanation for
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