In the present study, we investigated the effect of sumoylation on ALS-linked mutant SOD1 proteins in a motor neuron cell line and found that SOD1 is sumoylated not only by SUMO1 but also by SUMO2/3, suggesting a role for SUMO2/3 in the pathogenesis of ALS. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.