Protrudin is a known binding partner of spastin (i.e., SPG4), an ER-resident protein that bridges ER-lysosome contacts via its binding partner IST1 (Allison and others 2017) and whose dysfunction is causally involved in the most common form of HSP, a group of inherited neurologic disorders with more than 80 associated genetic loci (Blackstone 2018). The gene discussed is SPAST; the disease is nervous system disorder.