SOD1 and amyotrophic lateral sclerosis: The underlying mechanism by which misfolding and aggregation of SOD1 leads to the degeneration of MNs in ALS is still unknown, yet various hypotheses have been proposed, including disruption of axonal transport, mitochondrial dysfunction, inhibition of the ubiquitin–proteasome system, glutamate excitotoxicity, and caspase-mediated apoptosis and inflammation [252].