SOD1 and amyotrophic lateral sclerosis: Mutated or misfolded SOD1 decorates the surface of exosomes [18,232] and can transfer these toxic elements to healthy cells, as observed with exosomes carrying HuSOD1G127X or misfolded SOD1 [232], suggesting the capacity for mutant and/or misfolded SOD1 containing exosomes to participate in the spread of ALS.