ATP-dependent microtubule severing protein. Stimulates microtubule minus-end depolymerization and poleward microtubule flux in the mitotic spindle. Regulates microtubule stability in the neuromuscular junction synapse. Involved in lipid metabolism by regulating the size and distribution of lipid droplets. Involved in axon regeneration by regulating microtubule severing. n ATP + n H2O + a microtubule = n ADP + n phosphate + (n+1) alpha/beta tubulin heterodimers. Homohexamer. The homohexamer is stabilized by ATP-binding. The homohexamer may adopt a ring conformation through which microtubules pass prior to being severed. Interacts with microtubules. Interacts with atl; may be involved in microtubule dynamics. Forms an intramembrane hairpin-like structure in the membrane. Colocalizes with cellular microtubule arrays. Localizes to chromosomes from prometaphase/metaphase to anaphase, and this requires microtubules. Localizes to discrete punctate cytoplasmic foci which may correspond to secretory vesicles. Belongs to the AAA ATPase family. Spastin subfamily.