PSMF1 and amyotrophic lateral sclerosis: Genome-wide association studies have linked PI31 to AD risk (Sherva et al., 2011), and a direct antagonist of PI31, called valosin-containing protein (VCP), causes a familial type of the neurodegenerative disorder amyotrophic lateral sclerosis (Johnson et al., 2010; Clemen et al., 2015).