Recognition of C-terminal amino acids in tubulin by pore loops in Spastin is important for microtubule severing.

Spastin, an AAA ATPase mutated in the neurodegenerative disease hereditary spastic paraplegia, severs microtubules. Many other AAA proteins form ring-shaped hexamers and contain pore loops, which project into the ring's central cavity and act as ratchets that pull on target proteins, leading, in some cases, to conformational changes. We show that Spastin assembles into a hexamer and that loops within the central pore recognize C-terminal amino acids of tubulin.

Interaction of two hereditary spastic paraplegia gene products, spastin and atlastin, suggests a common pathway for axonal maintenance.

Hereditary spastic paraplegia (HSP) is a neurodegenerative disorder that is characterized by retrograde axonal degeneration that primarily affects long spinal neurons. The disease is clinically heterogeneous, and there are >20 genetic loci identified. Here, we show a physical interaction between spastin and atlastin, two autosomal dominant HSP gene products.

Linking axonal degeneration to microtubule remodeling by Spastin-mediated microtubule severing.

Mutations in the AAA adenosine triphosphatase (ATPase) Spastin (SPG4) cause an autosomal dominant form of hereditary spastic paraplegia, which is a retrograde axonopathy primarily characterized pathologically by the degeneration of long spinal neurons in the corticospinal tracts and the dorsal columns. Using recombinant Spastin, we find that six mutant forms of Spastin, including three disease-associated forms, are severely impaired in ATPase activity. In contrast to a mutation designed to prevent adenosine triphosphate (ATP) binding, an ATP hydrolysis-deficient Spastin mutant predicted to remain kinetically trapped on target proteins decorates microtubules in transfected cells.