Copper-dependent oxidative stress, alteration of signal transduction and neurodegeneration in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) occurs both sporadically and as a familial disorder (FALS); sporadic and familial forms are clinically indistinguishable and most probably share converging pathogenetic mechanisms. Present evidence indicates that ALS is multifactorial (1), like other late-onset neurodegenerative diseases in which loss of neurones reflects a complex interplay between oxidative i n j u r y, excitotoxic stimulation, dysfunction of critical proteins and genetic factors. The only gene conclusively linked to FALS so far, is the one coding for Cu,Zn superoxide dismutase (SOD1), an enzyme typically involved in intracellular defence against reactive oxygen species (ROS). More than sixty point mutations in the gene sod1, distributed in all the five exons, have been reported in about 20% of all FALS families (2). Mutations in s o d 1 do not cause FALS through simple loss of dismutating activity as originally proposed (3); several lines of evidence indicate that mutant SOD1s are responsible for the death of motoneurons through the acquisition of novel toxic properties, involving imbalance of ROS. The role of free radicals in ALS has been conclusively demon-