Serine protease inhibitors of the serpin superfamily are involved in many cellular processes. Neuroserpin was first identified as a protein secreted from the axons of dorsal root ganglion neurons. It is a member of the serpin superfamily of serine proteinase inhibitors. Neuroserpin is primarily secreted by axons in the brain, and preferentially reacts with and inhibits tissue-type plasminogen activator. It is thought to play a role in the regulation of axonal growth and the development of synaptic plasticity. Mutations in this gene result in familial encephalopathy with neuroserpin inclusion bodies (FENIB), which is a dominantly inherited form of familial encephalopathy and epilepsy characterized by the accumulation of mutant neuroserpin polymers. Multiple alternatively spliced variants, encoding the same protein, have been identified.