SOD1 and amyotrophic lateral sclerosis: ALS mutant SOD1 has been shown to directly interact with the 19S regulatory subunits of the proteasome, which could contribute to the observed proteasomal inhibition seen in multiple models of ALS (Urushitani et al., 2002; Kabashi et al., 2004; Cheroni et al., 2005, 2009).